– By Richard Gott / MemberWise Network Founder & Chair
– Membership Sector Influencer & Thought Leader

The MemberWise Network represents over 8,000 professionals employed by 2,500 leading membership organisations and associations in the UK, European Union (EU) and beyond. We proudly host the official list of the largest and most influential membership organisations in the UK.

Frequently Asked Questions (FAQs):

The Influence 100 is the list of the largest and most influential membership organisations based in the United Kingdom. The list is ranked by total membership size and is updated annually by the MemberWise Network. The latest version of the list features below.

There are over 8,000 membership organisations and associations based in the United Kingdom (with memberships of over 1,000 individuals/organisations). The figure for smaller organisations (including local sports clubs and societies) is likely to be far higher at approximately 50,000.

Over 80% of membership organisations and associations based in the UK are located in Central or Greater London with many (particularly those representing professions/trades and/or responsible for lobbying activity) are based there due to the traditional requirement to be close to central government.

The UK has an estimated population of 68.7 million citizens and it is estimated that at least 55m belong to some kind of membership organisation/association either:

– Retail (e.g. loyalty card)
– National (e.g. The National Trust
– Local (e.g. local church/library)

Circa. 14 million British citizens belong to over 450 professional membership organisations (of which 145 are Chartered Bodies) and there are 160 trade unions representing an estimated 8 million individuals (5.6 million are members of unions affiliated to the Trade Union Congress).

We estimate there to be over 50,000 membership organisations and associations based (with over 1,000 members) in the European Union. Over 1,500 are based in Brussels alone. The figure for smaller organisations is likely to be far higher at approximately 250,000.

In the United States of America (USA) there are a total of 22,200 associations and 115,000 with state, regional or local scope. There are 22,300 multinational, binational, and non-US national associations. The majority of associations in the US have headquarters in Washington, New York, or Chicago.

Back in 1996 the average Briton belonged to six membership organisations and according to a YouGov poll in 2006 this number increased to an average of 17. The poll also indicated that the fastest expanding membership organisations are online communities (with growth from 2.8 million to 72 million in just one year) and that the average adult belonged to 8.

The YouGov poll also indicated that the average adult belonged to two community organisations (e.g. local public library and a faith group) and three retail organisations (e.g. Nectar, Tesco Clubcard, the AA and Boots Advantage Card). The biggest of these entities being the AA and the Boots Advantage Card scheme which have memberships of approximately 14.4 million members.

MemberWise estimates the average UK citizen spends  approximately £60 per month (or £720 per year) on subscriptions like Netflix/Amazon Prime. An average monthly gym membership costs between £35 and £50 per month (or between £420 and £600 per year) and the average annual professional body/trade association membership is approximately £21 per month (or £252).

Based on the diversity of the organisations that feature on our list most have seen increases, however more recently some have seen a decline due to the Corona Virus pandemic.

On average our list shows a 10% increase (averaging 1.25% growth per annum), however there are some that have seen significant decline.

For example in 1979 UK trade union membership topped 13.2 million members, however this number has declined to 6.23 million members over the past 4 decades. The knock-on effect of this drop has seen membership of the Trade Unions Congress (3rd largest membership organisation on our list) decline by over 50% (from 12.2 million members to 5.7 million members).

Membership of the main political parties (most featuring in our list) have seen a 25% decline since 1964.

The Largest 100 UK Membership Bodies (Influence 100) List (2026)

2025 Rank2026 RankMembership OrganisationMembers 2025Members 2026Change
11National Union of Students (NUS) 6,300,000 6,200,000 (100,000)
32National Trust 5,364,000 5,327,000 (37,000)
43Unison 1,269,500 1,296,000 26,500
54English Heritage 1,180,000 1,180,000 -
75Unite 1,100,000 1,177,500 77,500
66Royal Society for the Protection of Birds (RSPB) 1,150,000 1,160,000 10,000
87Caravan and Motorhome Club 1,000,000 1,000,000 -
98Wildlife Trusts (46 in total) 944,500 945,000 500
109England Golf 730,000 836,000 106,000
1110Royal Horticultural Society (RHS) 610,000 625,000 15,000
1211The Scout Association 595,000 591,000 (4,000)
1412GMB 500,000 576,000 76,000
1313Camping and Caravanning Club 575,500 539,000 (36,500)
1514Royal College of Nursing (RCN) 500,000 500,000 -
1615National Education Union 497,500 497,500 -
1716u3a 405,000 422,000 17,000
1817British Gymnastics 400,000 416,000 16,000
2018Union of Shop Distributive and Allied Workers (USDAW) 368,500 372,500 4,000
1919Girlguiding UK 381,000 372,000 (9,000)
2220National Trust for Scotland 329,500 338,000 8,500
2121Oddfellows 344,000 318,000 (26,000)
2522Woodland Trust 300,000 300,000 -
2723Reform UK 220,000 268,000 48,000
2624Association of Chartered Certified Accountants (ACCA) 252,500 258,000 5,500
2325Labour Party 309,000 250,000 (59,000)
2426NASUWT 300,000 228,000 (72,000)
2827Law Society of England and Wales (TLS) 200,000 223,000 23,000
#N/A28Chartered Management Institute (CMI) 230,000 220,000 (10,000)
3729Institute of Chartered Accountants of England and Wales (ICAEW) 208,000 210,000 2,000
2930British Medical Association (BMA) 194,000 200,000 6,000
3831United Grand Lodge of England 170,000 200,000 30,000
9232Green Party 60,000 200,000 140,000
3133Public and Commercial Services Union (PCS) 186,000 189,000 3,000
3234Communication Workers Union (CWU) 185,000 185,000 -
3335Royal British Legion (RBL) 183,500 184,500 1,000
3436Wine Society 182,000 184,000 2,000
3937England Athletics 169,500 181,500 12,000
3038Historic Environment Scotland 188,000 181,000 (7,000)
3639Wildfowl and Wetlands Trust 173,000 178,000 5,000
3540National Federation of Women’s Institutes 180,000 170,000 (10,000)
4041Historic Royal Palaces 168,000 168,000 -
4142Chartered Institute of Personnel and Development (CIPD) 162,000 165,000 3,000
4443North of England Zoological Society (Chester Zoo) 155,000 165,000 10,000
4244Prospect (Union) 160,000 163,000 3,000
4345Institution of Engineering and Technology (The IET) 157,000 157,000 -
5146Tate Museum 142,500 153,500 11,000
4647RNLI 150,000 150,000 -
4748British Association for Shooting and Conservation (BASC) 150,000 150,000 -
4549Boundless (CSMA) 153,000 143,000 (10,000)
4950Campaign for Real Ale (CAMRA) 145,000 143,000 (2,000)
5251Art Fund 142,000 142,000 -
4852England and Great Britain Hockey 146,500 140,000 (6,500)
5053Police Federation of England and Wales 145,000 140,000 (5,000)
5354RBG Kew 138,500 139,500 1,000
6055Forestry England 122,000 135,000 13,000
6556Royal Institution of Chartered Surveyors (RICS) 113,000 130,000 17,000
5657Countryside Alliance 125,000 128,000 3,000
5758British Horse Society (BHS) 124,500 125,500 1,000
6359Chartered Insurance Institute (CII) 121,000 121,000 -
6460All England Netball 119,500 121,000 1,500
5461Conservative Party 131,500 120,000 (11,500)
5962Youth Hostels Association (England and Wales) 123,000 120,000 (3,000)
6263University and College Union (UCU) 121,000 120,000 (1,000)
5864Institute of the Motor Industry (IMI) 123,500 114,000 (9,500)
5565British Cycling 125,000 112,000 (13,000)
6766National Residential Landlords Association (NRLA) 110,000 112,000 2,000
6167Civil Service Sports Council (CSSC) 121,500 111,000 (10,500)
6668Institution of Mechanical Engineers (IMechE) 110,000 110,000 -
7869National Governance Association 80,000 110,000 30,000
6970Ramblers 103,500 106,000 2,500
6871Royal Yachting Association (RYA) 103,500 101,000 (2,500)
7072World Wildlife Fund (WWF) 100,000 100,000 -
7173Institution of Civil Engineers (ICE) 97,000 97,000 -
7374Spotlight 90,000 90,000 -
7475Arts Society (NADFAS) 90,000 90,000 -
7276Historic Houses 93,000 88,000 (5,000)
7777British Mountaineering Council 85,000 81,000 (4,000)
7578Liberal Democrats 86,500 80,000 (6,500)
7679MotorSport Uk 85,000 79,500 (5,500)
8080British Association for Counselling and Psychotherapy (BACP) 74,000 77,000 3,000
7981Paddle UK 75,000 75,000 -
8182British Computer Society (BCS) 71,000 70,000 (1,000)
8283Cycling UK 70,000 69,000 (1,000)
8484Chartered Society of Physiotherapy (CSP) 65,000 67,000 2,000
8385IAM RoadSmart 70,000 65,000 (5,000)
9086British Psychological Society (BPS) 61,000 61,000 -
8987Coeliac UK 61,500 60,500 (1,000)
8588Royal Air Forces Association 64,000 60,000 (4,000)
8789Educational Institute of Scotland 62,500 60,000 (2,500)
8690Chartered Institute of Procurement and Supply (CIPS) 64,000 60,000 (4,000)
9491CADW 58,000 58,000 -
9392Crohn’s & Colitis UK 59,500 58,000 (1,500)
9593Royal College of General Practitioners (RCGP) 56,000 57,000 1,000
9194Scottish National Party 60,000 56,000 (4,000)
8895Royal Society of Chemistry (RSC) 62,000 54,500 (7,500)
#N/A96Royal Institute of British Architects (RIBA) 52,000 52,000 -
#N/A97Chartered Institute of Securities and Investment (CISI) 52,000 52,000 -
9898Association of Accounting Technicians (AAT) 51,000 51,000 -
9799Chartered Institute of Building (CIOB) 52,000 51,000 (1,000)
96100English Bridge Union 54,000 50,000 (4,000)
34,547,500 34,783,500 236,000

(c) MemberWise 2026 (List Updated: 01/07/2026)

The Influence 100 List (2025) Entry Criteria

Our current criteria for entry on to the list is that membership bodies should have a UK Headquarters and membership is optional in return for a membership fee.

– A headquarters based in the United Kingdom

– Membership is optional and charged for directly via an annual membership fee

– Over 50% of members (voting or equivalent) live or work in the UK

What is the role and purpose of the MemberWise Network?

As the leading free professional network for membership and association professionals we support circa 8,000 professionals working in over 2,500 medium/large membership organisations and associations.

2/3rds of our members work within medium/large professional bodies (individual membership) and 1/3 represent leading trade associations (corporate membership). We also represent other types of membership organisations and associations outlined here.

The network enables membership and association professionals (at all levels and career stages) to:

– Increase new member acquisition
– Improve existing member retention
– Optimise and develop member engagement
– Enhance member value
– Facilitate greater member participation
– Enable sustainable long-term growth

This is achieved via practical tools and resources including our comprehensive website (www.memberwise.org.uk), our growing programme of conferences and seminars, our thriving online community (MemberWise Connect), MemberWise Learn (our online learning portal), MemberWise Recognised Supplier Directory, membership sector research reports & publications, weekly newsletter and Jobs Board.

These resources are supplemented by a range of advisory, consultancy and membership focused training services (view membership body case studies/clients).

Join our free and growing professional network today!

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