The Liberal Democrats’ newest MP, Sarah Wollaston, has said a temporary Jeremy Corbyn led government would be “the lesser of two evils” in order to prevent a no-deal Brexit, but added she believed it would have no chance of support from former Tory colleagues.

Wollaston’s remarks go further than those of her party leader, Jo Swinson, who on Thursday stopped short of saying she would support a Corbyn-led interim administration.

The Totnes MP, who quit the Conservatives in February to join the breakaway Independent Group, said she backed the position of Swinson that Corbyn’s offer to lead a temporary government to halt no deal would never pass.

In an interview with the Guardian, Wollaston said there could be a “game-change” defection to the Lib Dems in the coming weeks which could eliminate Boris Johnson’s majority, and also proposed cancelling parliament’s three-week autumn recess in order to find ways to stop no deal.

She added she would be personally prepared to back Corbyn on a temporary basis as the only mechanism to stop no deal, even though she said she had no confidence in the Labour leader.

“Jeremy Corbyn is being a bit disingenuous here – he knows Conservative MPs are not going to vote confidence in Corbyn, they would be happy to vote no-confidence in Boris Johnson,” she said.

“But it’s much easier for them to vote for a more neutral, elder statement. All Jo is doing is stating the obvious that it simply won’t work. If the point is to get to vote of no confidence through, then it would be better for Corbyn not to link it so directly to his leadership. It kills it, completely.”

If Jo Swinson is serious about stopping a no-deal Brexit, she must support Corbyn | Jonathan Lis Read more

However, Wollaston said she could grudgingly back the Labour leader’s efforts to stop no deal, but felt her own vote would make no difference to the parliamentary arithmetic.

“Frankly, I don’t have confidence in Corbyn but for me the bigger picture here is we have to register as a parliament we want to stop no deal,” she said. “Ultimately it doesn’t matter what I would do, it’s about what Tory MPs would do.

“Obviously, as the lesser of two evils, I would have to make a judgment and probably say: you know what, I think it would be worse to have no deal. But you need five or six Tories to do it, and I’m sorry but they are just not going to do it. But they could vote for a strictly time-limited elder statesman who could command broader support, there are plenty of those figures around.”

Wollaston said MPs should be prepared to block a parliamentary recess in the autumn, the traditional time when MPs hold their party conferences, in order to buy more time in parliament to find a mechanism to stop no deal.

“Those three weeks are very precious and I don’t think we can justify conference recess,” she said.

Wollaston, a former GP who chairs the health select committee, is the second former member of Change UK to join the Lib Dems after former Labour MP Chuka Umunna, who is likely to be more instinctively hostile to any action which could put Corbyn in Downing Street.

Wollaston, who has been planning her leap to the Lib Dems for some months, said she had always been in two minds about forming a new party to fight in the European elections and said the public had “delivered their verdict”, that it needed remainers to unite behind one party.

“We want a unified voice for remain, and I didn’t think it would be right to put our energy into anything else,” she said. Wollaston was keen to wait until Swinson had been confirmed as leader of the party, due to their close personal relationship, and said joining the party felt like she had “come home”.

However, she acknowledged it could be more difficult for former Conservative colleagues to leave their party. At least one Tory MP, the former justice minister Philip Lee, has suggested he wouldspend the summer considering whether to join the party, a move that would eliminate Johnson’s majority.

“It would be a game-changer,” Wollaston said. “I do hope it will happen by the time we return.”

Wollaston said more defections from the Conservatives could have a significant effect on Downing Street, as she believed did her departure party along with fellow former Tory MPs Heidi Allen and Anna Soubry.

“They were worried about a mass exodus and they rowed back from no deal,” Wollaston said. “I think we did have an impact by leaving and what I would like to see is that same impact applied to Boris Johnson.”

The MP said she was unconvinced Johnson could call a snap election to be held over 31 October, in order to prevent MPs from stopping the UK leaving with no deal and slammed the prime minister for his appointment of the former Vote Leave boss Dominic Cummings as his de-facto chief of staff.

“Can you imagine the instability of us coming out of the European Union, with all its disruption, but with no accountability mechanism for six weeks?” she said.

“This is all Dominic Cummings, a man who is now Boris’s right-hand man and who has been found in contempt of parliament. This is the person who is the puppet master in No 10. It’s an outrage.”

Wollaston said she would welcome a general election, and would even be prepared to stand aside for a Green party candidate in Totnes if the party stood more chance of winning the seat.

“If I held a byelection, I’d have six weeks during this crucial period of no say at all for Totnes and hand the government’s majority a boost,” she said. “I’d prefer to have a general election in order to have legitimacy.

“I am not proprietorial and I know all parties need to be generous. There needs to be a process of all the parties looking at the data and see how we can best not split the vote. If I get the opportunity, I will definitely stand but it has to be a unity candidate or none of us will win.”