By law, all trade unions that hold a political fund must ballot their members every ten years. Prospect's ballot is the first of a series of trade union ballots to take place on whether to keep a political fund or not.

Prospect General Secretary Mike Clancy said: "When we balloted a decade ago the result was very tight. Just 50.2% supported the political fund, a majority of 134 votes. This time, 40,400 members - over 91 per cent - voted in favour of a political fund, compared to 21,537 in 2003.

"I think this sends a clear message about how our members, who are representative of the 'squeezed middle' in society, are hurting. The cost of living is rising, yet their pay and pensions are under attack. Job insecurity is greater, and their workplace rights are being eroded.

"I believe members are saying they want us to use the political fund to raise their concerns on these issues. I hope politicians will take note of the scale of this result in a trade union that is not militant and not affiliated to any political party. It is a very significant result."

Clancy said he wanted to thank everybody who helped organise the ballot, all those who campaigned for a high turnout and a positive result, and all the members who voted.

• The ballot was conducted in accordance with the Trade Union and Labour Relations Act 1992. Other trade unions will be holding their ballots in the coming weeks and months.

• In total 40,400 members (91.3%) voted to retain the political fund, 3,865 voted against (8.7%) and 77 votes were spoiled or ruled invalid. The turnout was 37.6%.