Jeremy Corbyn is poised to reject Boris Johnson’s demand for a 15 October election for a second time on Monday, with Labour fearing it would play into the prime minister’s hands.

Despite being taunted by Johnson as a “chlorinated chicken” who is afraid of facing the public, Corbyn is holding out for an election on Labour’s own terms – most likely at a later date.

The government has suggested that it will hold a vote on another motion under the Fixed-Term Parliaments Act on Monday, a procedure that requires two-thirds of MPs to back it if it is to pass.

Labour had considered whether it could amend the motion in order to fix the election date, to prevent Johnson changing it in order to force through a no-deal Brexit – but has been advised that any amendments would not have legal force.

The Guardian understands no final decision has been made about Labour’s tactics next week, but daily discussions are taking place with other key opposition figures including the SNP’s Ian Blackford and Liberal Democrat leader, Jo Swinson.

One option under fresh consideration is a vote of no confidence, which could be tabled as soon as next week. If the government lost, it would be followed by a 14-day period during which MPs could seek to put together an alternative majority.

As Corbyn proposed in the summer, he would then seek to lead a strictly time-limited government, which would simply request an extension from the EU27 for the purposes of holding a general election, and then dissolve itself.

Corbyn told MPs in the House of Commons on Wednesday that he would be ready to support Johnson’s call for a general election once the backbench bill aimed at preventing a no-deal Brexit has passed.

“Let this bill pass and gain royal assent, and then we will back an election so we do not crash out of the European Union with a no-deal exit,” the Labour leader said.

But one shadow cabinet minister close to Corbyn said senior figures in the party had been “agonising” over the best course of action. Another said they had been increasingly won over to the idea of refusing Johnson’s choice of polling date, as his short-lived administration appears to stumble. “They are imploding – a further delay might help us.”

John McDonnell acknowledged there were “different views” in Labour about the timing of a general election. “The problem that we have got is that we cannot at the moment have any confidence in Boris Johnson abiding by any commitment or deal that we could construct,” he told BBC Radio 4’s Today.

“That’s the truth of it. So, we are now consulting about whether it’s better to go long, therefore, rather than to go short.”

However, the president of the TUC, a close ally of Corbyn, called for Labour to support a general election as soon as legislation halting a no-deal Brexit is imposed upon the government. Mark Serwotka also warned Labour MPs including deputy leader Tom Watson to fall in line behind their leader.

Corbyn had faced a backlash after appearing to suggest he would back a 15 October general election without further conditions attached.

Wes Streeting MP said: “Our No 1 priority is stopping a no-deal Brexit happening during a general election campaign through accident or design. We don’t trust Boris Johnson and nor should anyone else. Once we are confident that no deal is safely ruled out, we will all troop through to vote for a general election, which is now necessary, inevitable and desirable.”

Fellow MP Andy Slaughter said he would vote against or abstain in a second government vote called to try and bring about an election unless he could get a copper-bottomed guarantee that the anti no-deal legislation tabled by the government was adhered to.

Serwotka, who was due to address the first day of the TUC’s annual congress in Brighton on Sunday, said he favoured going to the polls as soon as anti no-deal legislation was in place. “My position is that we want an election – we want it as soon as possible once a no-deal Brexit is off the table. We have been demanding a general election and now we should get to it as quickly as we could,” he told the Guardian.

“I think that having an election leaving Boris Johnson any opportunity to push through a no-deal Brexit by default would be ridiculous. I think [Johnson’s supporters] know that people aren’t going to fall for their trap. It would be outrageous if we slipped out of the EU while holding an election,” he said.

Serwotka, the general secretary of the PCS public service union since 2001, said the current political crisis should mean that Watson and others no longer “indulge” in plots or undermining tactics against Corbyn. “I think the dangers of perceived splits in the Labour party are damaging.

“The actions of some of the parliamentary Labour party such as Tom Watson and others have been really unacceptable. They must know as much as anyone else what is at stake. And I think there will be a demand to keep our eye on the ball here. Now is not the time to indulge in undermining Jeremy,” he said.

Watson has been criticised by Corbyn supporters for calling for greater cooperation with the Lib Dems to stop Brexit and for allegedly “exacerbating fears” over antisemitism within the party – claims that Watson’s allies deny.

Serwotka, who rejoined Labour under Corbyn’s leadership, dismissed the idea of a national unity government led by a parliamentary grandee, adding that he would only support a Corbyn-led government.