Jeremy Corbyn will only deliver the two-thirds Commons majority required to trigger a snap poll if legislation to block a no deal is “locked down” first, the party says.
Labour also fears Mr Johnson could be handed the election – and only then switch the date to after 31 October, when the UK would have left the EU.
“We are not daft enough to see a tactic dictated by PM Johnson which is designed to land us with a no-deal Brexit and to fall for that,” said Tony Lloyd, the shadow Northern Ireland secretary.
“Will we fall for Boris Johnson’s trick? No we won’t. Boris Johnson is a man who has got form for reneging on his promises.”
Shami Chakrabarti, the shadow attorney general, added: “We need a locked in guarantee that Britain will not crash out of the EU in an election campaign period.”
The caution throws a fresh hurdle in the prime minister’s plan to stage the third election in four years, if a cross-party alliance of MPs succeeds in passing legislation to prevent a Halloween crash-out.
The threat was briefed by No 10 late on Monday, despite Mr Johnson himself continuing to insist he does not want an election in his Downing Street address.
Under the Fixed-term Parliaments Act, two-thirds of all MPs must agree to a snap election. Even then, the prime minister has the power to change the election date by proclamation.
The backbench attempt to seize control of Commons business to pass a no-deal blocking bill is expected to succeed tonight, but the legislation may not clear the House of Lords until the weekend.
If Mr Johnson follows through on his 14 October election threat, the Commons could be asked to sanction it on Wednesday – before the legislation is “locked down”
In a rally in Salford, Mr Corbyn made clear he wanted an election, declaring “I’m ready for it, you’re ready for it, we’re ready for it”.
But, speaking on BBC’s Newsnight programme, Mr Lloyd said: “We will not have Boris Johnson dictating the terms of an election, which crashes this country out with a new deal Brexit.
“Obviously, once we can guarantee that we pass 31 October and don’t have a no-deal Brexit, of course we want an election.”
One plan is for Labour to try to attach the condition that polling day can only take place if an EU extension has been granted.
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