Trade unions
| Full Name | Short Name | Notes |
|---|---|---|
| British Medical Association | BMA | |
| British Orthoptic Society | BOS | |
| British Steel Smelters, Mill Iron & Tin Plate Workers Assoc | Steel | |
| Broadcasting, Entertainment, Cinematograph and Theatre Union | BECTU | |
| Card Setting Machine Tenters Society | CSMTS | |
| Ceramic and Allied Trades Union | CATU | |
| Chainmakers and Strikers' Association | CSA | |
| Chartered Society of Physiotherapy | CSP | |
| Chemical Workers' Union | ChWU | |
| Civil and Public Services Association | CSPA | |
| Civil Service | Civil Service | |
| Civil Service Clerical Association | CSCA | |
| Clerical and Administrative Workers' Union | CAWU | |
| Commercial Travellers' Association of Great Britain | CTAGB | a.k.a. United Kingdom Commercial Travellers' Association |
| Communication Workers Union | CWU | |
| Community | Community | |
| Community and District Nursing Association | CDNA | |
| Community and Youth Workers' Union | CYWU | |
| Confederation of Engineering and Shipbuilding Trades | CEST | |
| Confederation of Health Service Employees | COHSE |