Opposition leaders are still unable to agree on who should front a temporary government aimed at stopping no-deal Brexit.
Labour leader Jeremy Corbyn insists that he, as Leader of the Opposition, should take over if Boris Johnson is toppled by a vote of no confidence.
But Liberal Democrat leader Jo Swinson, also speaking after cross-party talks on Monday, flatly rejected the possibility that her MPs could back Mr Corbyn as an interim prime minister.
Ms Swinson said party whips would meet to discuss candidates to take over from the Prime Minister if he is ousted, but said the Labour leader cannot command support in the Commons.
“He simply does not have the numbers,” Ms Swinson said, referencing the 21 MPs exiled from the Conservative Party and the five within the Independent Group for Change (IGC).
“I have been crystal clear but I will do so again – Jeremy Corbyn is not going into Number 10 on the basis of Liberal Democrats’ votes.”
The Labour leader first outlined his plans in August for a no confidence vote followed by a temporary government under his leadership to secure an extension to Article 50 and then a general election.
And he remains resolute that he should be leader rather than other mooted candidates, such as veteran MP Ken Clarke or Dame Margaret Beckett.
In an interview on Monday, Mr Corbyn said: “The position is quite simply this: when a Government collapses then the Leader of the Opposition is invited to form an administration.”
The leaders – who met in Mr Corbyn’s office with the SNP’s Ian Blackford, Plaid Cymru’s Liz Saville Roberts and the IGC’s Anna Soubry – agreed not to hold a vote of no confidence this week.
Ms Swinson said any such move while the PM is at the Tory conference in Manchester would “play into Boris Johnson’s hands”.
Mr Corbyn said manoeuvres to force Mr Johnson to comply with the Benn Act, which orders the PM to ask Brussels for a delay if no Brexit deal is backed by MPs by October 19, remains on the table.
So also, he said, does seizing control of the Commons schedule to prevent a no-deal Brexit.
“There are no signs that the Prime Minister has even made an application of any sort, or indeed any proposals, to the EU thus far,” Mr Corbyn said.
Under his “do or die” commitment to enact Brexit by the current October 31 deadline, Mr Johnson has raised fears that he will not comply with the Benn Act.
He has repeatedly ruled out breaking the law, but there are suspicions he may try to circumvent the legislation to force through a no-deal exit.
The Supreme Court ruling that found the PM unlawfully prorogued Parliament with the Brexit deadline looming did nothing to quell opposition fears.