Margaret Beckett emerging as favourite to be caretaker prime minister, writes Robert Peston

Dame Margaret Beckett - the former Labour deputy leader and ex-foreign secretary - is emerging as the most likely compromise candidate to be caretaker prime minister, according to sources involved in opposition talks about ousting Boris Johnson.

As I mentioned last week, the Scottish National Party would be prepared to accept Jeremy Corbyn as temporary PM, with the express purpose of securing a three month Brexit delay and holding a general election.

But it has become clear in talks between the opposition parties that the Lib Dems and expelled or self-exiled Tory MPs won’t agree to install Corbyn as PM.

"We cannot win a vote of no confidence if Corbyn is the candidate," said a senior opposition MP.

"And there is no point having the vote if we are not guaranteed to win."

So there are exploratory talks to find a more unifying candidate, and Beckett has emerged as the front runner - because she is not seen by Corbyn and his close colleagues as a threat to his leadership.

That said, as I understand it Corbyn is yet to endorse the Beckett plan.

There is a growing concern among opposition MPs that if they fail to oust Johnson within days, he may outmanoeuvre them and secure the no-deal Brexit on 31 October they are desperate to prevent.