PCS has overwhelmingly voted to swing its weight behind Labour at next month’s general election.

At the Civil Service union’s annual conference in Brighton yesterday, delegates endorsed a motion pledging to “offer as much support to Labour Party candidates as is allowable under current NEC policy.”

It is the first time the union, which is not affiliated to any party, will have backed a major election campaign since its creation 19 years ago.

General secretary Mark Serwotka said: “For once we have a real alternative. Jeremy Corbyn offers a completely opposite way forward for Britain.

“Our members must understand that choice, so they don’t get diverted by the nonsense that is Brexit and strong and stable leadership, they ask themselves what is in their interests.

“There’s only one person who can be an alternative to Theresa May as Prime Minister, and that is Jeremy Corbyn.”

Delegates at the conference debated how far the union should go in supporting Labour.

A separate emergency motion proposed by the union’s executive welcomed Labour’s leftward shift under Mr Corbyn and said the election was an opportunity for the union to “step up our campaigning.”

But some delegates argued that the union should not shy away from more overt backing, successfully calling on the conference to endorse the more strongly worded motion as well.

“We should go further and make it clear we want a vote for Labour,” National Archives delegate Christopher Day said.

Greater Manchester delegate Annette Wright added: “We can go back and campaign for our policies, which is what we would do anyway, or we can go back and ask our members to vote Labour.”

But members in Scotland said any explicit backing for Labour across Britain could damage the union’s standing north of the border.

“Not only is this completely out of step with what members in Scotland want, it puts PCS in Scotland in an extremely difficult position,” Glasgow delegate Bobby Young said.

East Kilbride delegate Scott Clark said backing Labour would amount to “endorsing the Orange Order by proxy,” saying that the Scottish party was “not the same Labour Party.”

The executive’s motion said a Tory victory at the polls would be the “worst possible outcome.”

But Department for Work and Pensions east London delegate Tony McDonald said: “We should ask what’s the best possible outcome, and I think the best possible outcome is a Labour government.”