Jeremy Corbyn has signalled that Labour will back a snap election once the Commons approves radical legislation to block a no-deal Brexit.

The Labour leader revealed his hand immediately after Boris Johnson suffered a humiliating defeat on his very first vote since becoming prime minister.

A total of 21 Tory MPs rebelled against the government and were expected to have the whip withdrawn by their party.

But as the PM confirmed his next step would be to table a motion for a snap election, Corbyn made clear for the first time he would back the move – as long as an emergency bill to stop a no-deal Brexit was passed first.

Labour won’t vote for the Johnson motion on Wednesday, but it will change position once Hilary Benn’s bill to extend the UK’s membership of the EU becomes law. 

Some in the party hope that the bill will clear parliament as early as this Friday afternoon, though others expect it could occur at the weekend.

Corbyn told MPs: “As I have said before: if the prime minister has confidence in his Brexit policy – when he has one he can put forward – he should put it before the people in a public vote.

“And so, he wants to table a motion for a general election, fine. Get the bill through first in order to take no-deal off the table.”

The new position from the opposition – hammered out after intense internal talks – allows it to say it won’t fall into Johnson’s “trap election” where he could let Britain fall out of the EU by default on October 31.

Several MPs feared the PM could not be trusted to stick to his planned polling day of Tuesday October 15 and demanded a legal ‘lock’ to bind his hands.

Sources said that it would be upto Johnson to return with a fresh polling day demand. If he wants a mid-October election, next Monday may be his last chance to get one.

The new stance means that the party will vote for an election only once the Benn bill is secured.

However, Tory Brexiteer peers are lining up to scupper the bill if it gets to the House of Lords later this week.

More than 90 amendments have been tabled in a bid to bog down a Labour motion that seeks to set a cut-off deadline of Friday 5pm for the bill.

If the bill drags on through the weekend, it could be Monday before Labour agrees to any election proposal.

Labour MPs had warned their leadership not to fall into a ‘trap’ set by Johnson, and Chief Whip Nick Brown confirmed to a meeting of the Parliamentary Labour Party (PLP) on Tuesday that it would not do so.

Shadow Foreign Secretary Emily Thornberry told ITV News: “There won’t be a general election called tomorrow because we are not going to vote for it. Because we have to make sure that this legislation is embedded, signed off by the Queen and there’s no arguing about it any more.”

However, Thornberry appeared to suggest the election vote may not be ready until mid-October when the Commons is due to return after a suspension. It ‘prorogues’ from sometime next week, possibly as early as Monday, until October 14.

“It’s a question of getting the sequence right. First we stop no-deal. Then Boris is going to send us all away and not let us come back for a while. Then we will see,” she said.

HuffPost UK understands one plan is for Labour to table its own amendment to a Fixed Term Parliaments Act motion.

It would make any election date subject to a strict condition that the dissolution of parliament cannot occur until after the Benn bill gets Royal Assent from the Queen.