Jo Swinson has suggested either Ken Clarke or Harriet Harman become prime minister of an “emergency government” to stop a no-deal Brexit.

The Lib Dem leader has rejected Jeremy Corbyn’s plea that she help install him in Downing Street following a no confidence vote in Boris Johnson’s government in September.

Swinson said Corbyn would not be able to gain the support of a majority in parliament as even some Labour MPs do not want him to become prime minister.

But after Tory rebels agreed to at least sit down for talks with Corbyn, Harman indicated her support for the Labour leader’s approach, while not ruling out becoming PM herself.

A Lib Dem source meanwhile insisted that Harman had told Swinson she would step up if asked.

The source stressed that the Lib Dems could end up backing Corbyn if he demonstrated he could command a majority but Swinson regarded it as “unrealistic”.

But earlier at a press conference in London, Swinson said: “He is demanding the keys to No.10 as a precondition for a vote of no confidence.

“If he is serious about wanting to stop no-deal he needs to understand that the way to do that is with a figure leading an emergency government who is not divisive.”

Swinson said she would do “whatever it takes” to stop no-deal Brexit and said her preferred option was to change the law to hold a second referendum.

“We are facing a national crisis. We may need an emergency government to resolve it,” she said.

“If Jeremy Corbyn truly wants that to succeed, surely even he can see that he cannot lead it.

“What we need in a leader of an emergency government is a long-serving MP who is respected on both sides of the House.

“Someone like Ken Clarke or Harriet Harman, the father and mother of the House, they are hugely experienced.”

Swinson argued they would be best suited as neither was “seeking to lead a government in the long term”.

Clarke, the veteran pro-EU Tory, is the longest serving MP. Harman, the former deputy Labour leader, is the longest serving female MP.

Swinson received a boost yesterday when former Tory and Change UK MP Sarah Wollaston defected to the Lib Dems.

Last night Corbyn wrote to Swinson and other opposition party leaders to ask them to back him for PM until a general election could be held in order to prevent a no-deal.

The Labour leader said the administration would be “strictly time-limited” and that he would seek an extension to the Article 50 process to delay the UK leaving the EU past the October 31 deadline.

“This government has no mandate for no-deal, and the 2016 EU referendum provided no mandate for no-deal,” he said.

“I therefore intend to table a vote of no confidence at the earliest opportunity when we can be confident of success.”

The SNP’s Ian Blackford welcomed the Labour leader’s letter and said the party would bring down the Tories in a no-confidence vote.

Plaid Cymru’s Liz Saville Roberts also offered her cautious support, saying the party is open to a unity government regardless of who leads it, but that it must have “stopping Brexit” as its first priority.

Green Party MP Caroline Lucas, another recipient of the letter, also said she would back a no-confidence vote, but added that she wants Corbyn to guarantee Labour’s support for another MP to lead a temporary Government if his bid to govern fails.