THE “natural constitutional process” is that Jeremy Corbyn becomes prime minister if Boris Johnson’s government falls, Labour shadow international trade secretary Barry Gardiner said today.

He told Sky News that Lib Dem leader Jo Swinson was being “extremely petulant” for dismissing Mr Corbyn’s plan to become “caretaker PM” to prevent a no-deal Brexit on October 31.

Mr Corbyn is expected to launch a vote of confidence in Mr Johnson’s government, which has a majority of just one, in the coming weeks in the hope to force a general election.

The Labour leader has written to the Lib Dems, Green, SNP, Plaid Cymru, Change UK and Tory back-bench MPs urging them to “do everything we can to stop” Britain heading into “a constitutional and political storm.”

But Ms Swinson has claimed that he would be unable to bring together enough MPs to support his proposal and that she would prefer Tory Ken Clarke or Labour’s Harriet Harman to be “caretaker PM.”

Mr Gardiner said that the Queen would be forced into a “very embarrassing and difficult judgement call” if she was propelled to invite someone other than Mr Corbyn to form a new government.

He added: “It sounded as if [Ms Swinson] couldn’t take yes for an answer.

“The Liberal Democrats and others have been saying for so long: ‘Look we need to have a second referendum and Remain needs to be on the ballot paper.’

“They are now being offered a failsafe parliamentary procedural way of delivering that and they’re saying: ‘Oh, we’re not going to co-operate if Jeremy Corbyn is going to be the person who does it’.”