Trade union leader Mark Serwotka banned from voting in Labour leadership election

The PCS general secretary has had his ballot cancelled

Mark Serwotka, general secretary of the PCS trade union (AFP/Getty)

The leader of one of Britain’s major trade unions has been banned from voting in the Labour Party’s leadership election.

Mark Serwotka, the general secretary of the PCS union, which represents civil servants, had his ballot retroactively revoked after having voted online earlier this month.

The trade unionist was a member of the Labour party until the 1980s; his union says he has not been a member of another political party since.

Ruth Serwotka, Mr Serwoka’s partner, tweeted that the decision was “a total joke” and posted photos of him campaigning with leadership frontrunner Jeremy Corbyn.

Labour officials are working to "purge" the party electorate of people who they believe do not agree with its aims and values.

Labour leadership hopefuls, from left, Yvette Cooper, Liz Kendall, Andy Burnham and Jeremy Corbyn on the BBC (PA)

A source close to Mr Serwotka told the Independent: "Mark has spent his life arguing and campaigning for workers' rights, equality, a fairer distribution of wealth and an end to poverty and discrimination, and in recent years has been at the forefront of the fight against austerity. Which of these are not aims and values shared by the Labour party in 2015?"

Mr Serwotka sits on the general council of the Trades Union Congress (TUC). He has previously voted for other parties and expressed support for other left-wing groups.

His exclusion is likely to be controversial because trade unions have long been considered part of the core values of Labourism.

The PCS is not formally affiliated with the Labour party and Mr Serwotka has previously suggested supporting left-wing candidates from across parties on an individual basis.

But after Mr Corbyn announced his candidacy, Mr Serwoka said he would consider advocating affiliating Britain’s sixth biggest union to Labour.

“If Jeremy Corbyn wins, that would change everything… We wouldn't rush into affiliating but would want to work very closely to develop policy together – and if that goes well then let's see where we end up,” he told the Financial Times at the time.

The trade unionist in 2010 criticised the previous Labour government for being the “worst” employer he had dealt with, but said before the last election that Conservative and Liberal Democrat ministers had been even worse. He said at the time that he wanted Labour to win the election.

Labour on Tuesday said it had booted out 3,000 “cheats” who did not agree with the aims and values of the party.

“Those people who don’t support the aims and values of the Labour party are not entitled to vote. We will continue the process of verification right up until the last minute,” acting leader Harriet Harman told BBC News.

The party says the 3,138 people excluded for breaking its rules included 400 Conservatives, some of whom have said they would try to vote for candidates they consider weak in order to undermine the Labour party.

1,900 Green Party supporters have also been excluded. A large number of Greens have said they have been attracted to vote in the contest because they like left-wing candidate Jeremy Corbyn.

This morning on BBC Radio 5Live Mr Corbyn said any influx of genuine supporters should be welcomed “because that's how parties grow".

The PCS trade union confirmed that Mr Serwotka had been barred from the contest.

A Labour spokesperson said they would not discuss individual cases.

Voting in the contest is underway, with the winner announced at a special party conference in September.