Labour’s leadership is determined to hold out against backing a second referendum on Brexit unless all other options have been exhausted, despite growing calls for the party to tack towards remain, according to senior party sources, amid reports that Theresa May could seek a TV debate with Jeremy Corbyn.

The Labour leader’s close allies are acutely conscious they may have to make momentous decisions at high speed if May’s deal is rejected by MPs in the meaningful vote expected to be held on 12 December: a scenario that looks increasingly likely.

The prime minister would have to return to parliament within 21 days and set out how she intended to proceed.

Labour sources say they would probably wait to see what she proposed before tabling a vote of no-confidence, in the hope of triggering a general election. “We’ll only get one shot at this,” one party strategist said.

If the bid to trigger an election fails, “all options are on the table”, according to the motion hammered out at the party’s conference in Liverpool in September.

But Labour strategists believe they cannot get to the 45% or so of the vote they would need to win the next election if they are seen to represent only what they jokingly refer to as “Remoania”.

Monday’s Daily Telegraph reported that May would seek a TV debate with Corbyn on her Brexit deal as the showpiece of an election-style campaign to seek the country’s backing before the parliamentary vote. A Labour party spokesperson said: “Jeremy would relish a head-to-head debate with Theresa May about her botched Brexit deal and the future of our country.”

Some hold out the hope that Labour could pick up many of the leave-backing voters who feel sold out by the prime minister’s deal.

“They’re available to us provided we don’t sound like remainers,” one shadow cabinet minister said, adding that the party must also guard against the risk that these voters switch to Ukip.

In the run-up to the 2017 general election, Labour’s then-pollsters, BMG, suggested the party needed to sound pro-Brexit, or risk alienating voters in a swath of heartland constituencies, two senior Labour figures who saw the report have told the Guardian – one of whom added: “We don’t think the picture’s changed that much since.”

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In Corbyn’s inner circle, the shadow home secretary, Diane Abbott, has told friends she is on a “vigil” against any move that could alienate Labour supporters in staunchly remain seats such as her constituency of Hackney North and Stoke Newington. However, the Hemsworth MP Jon Trickett is more exercised about the anxieties of northern leave voters.

Labour’s determination to reject May’s Brexit deal when she brings it back to Westminster has been bolstered by private polling showing only 21% of voters believe it will be better than EU membership.

Internal research is telling the party that 42% of voters think the deal negotiated by the prime minister will be worse than staying in the EU; against only 21% who believe it will be better. Voters have also told Labour’s pollsters – by a two to one margin – that they supported MPs’ right to vote it down if they thought it was damaging for the country.

“This is a bad deal for the country,” said Corbyn on Sunday. “It is the result of a miserable failure of negotiation that leaves us with the worst of all worlds. It gives us less say over our future and puts jobs and living standards at risk.

“That is why Labour will oppose this deal in parliament. We will work with others to block a no-deal outcome and ensure that Labour’s alternative plan for a sensible deal to bring the country together is on the table.”

However, the majority of the public also say they want Brexit to be over and done with – a sentiment the prime minister has been keen to play on as she ramps up Downing Street’s bid to sell the deal to a wary public.

Facebook Twitter Pinterest Shadow home secretary Diane Abbott: ‘My view is that if we had a second referendum tomorrow, leave would win again.’ Photograph: Ian Forsyth/Getty Images

Nevertheless, a growing number of frontbenchers believe Labour may need to “swerve” towards a “people’s vote”, as one put it, if public opinion swings behind the idea; and the leadership will come under intense pressure from the party grassroots to do so.

Labour’s deputy leader, Tom Watson, said recently it was “more likely given the weakness of Theresa May’s position”.

Abbott is among those shadow cabinet members who have publicly expressed concern about the risks of a second referendum. She told the BBC’s Nick Robinson last week: “People should be careful what they wish for, because my view is that if we had a second referendum tomorrow, leave would win again and not only would leave win again but leave voters would say ‘What didn’t you understand about leave winning the first time?’”

Keir Starmer, who said publicly last week he would vote remain if a second referendum were held, is keen to ensure the parliamentary Labour party is united behind any shift in policy.

A general election would risk exposing the bitter tensions within the party about Brexit. The leadership is clear it would want to go into an election promising to press ahead with leaving the EU, but strike a less economically damaging deal.

But a vocal cohort of Labour MPs could find it impossible to stand on a manifesto that did not state stopping Brexit as an aim. One MP campaigning vigorously for remain said: “I think it would rip the party apart, simple as that.”

A small number could even seek to split from Labour and stand as “stop Brexit” independents. Some of Corbyn’s closest lieutenants are relaxed about that happening, believing official Labour candidates would beat them.