The Labour leader said there is ‘no process other than the leader of the opposition being invited to form that government’ in the event that Mr Johnson is toppled.
The remarks will almost certainly reignite a bitter row among Mr Johnson’s critics over who should be allowed to try to form a government of national unity.
Mr Corbyn is adamant that it must be him but the
Lib Dem sources suggested Mr Corbyn’s latest remarks demonstrated a lack of understanding of how a new government would be set up if the current administration was to fall.
His comments also appear to assume that Mr Johnson would resign as Prime Minister and make way for a new government if he loses a vote of no confidence.
Downing Street sources have previously suggested that he would not quit in such circumstances and would instead try to force an early election.
Jeremy Corbyn, pictured during a visit in Southampton today, said if Boris Johnson loses a vote of no confidence he would be ‘invited to form an administration’.
The Labour leader’s remarks suggest he believes the Queen, pictured near Balmoral on October 6, would automatically ask him to be PM if Mr Johnson is ousted
According to comments reported by The Guardian, Mr Corbyn said today he would form the next government if Mr Johnson loses a vote of no confidence.
That government would then have a single task of stopping a No Deal Brexit.
He said: ‘A caretaker government would be one appointed on the basis that the government has collapsed and the leader of the opposition is invited to form an administration.
‘When this government collapses I will accept that invitation and form an administration solely for the purposes of preventing a crash-out.
‘There is no process other than the leader of the opposition being invited to form that government and that’s what we will follow.’
Mr Corbyn’s comments suggest he believes the Queen would ask him to be PM if Mr Johnson is ousted.
However, under the Fixed-term Parliaments Act 2011 a successful vote of no confidence would simply trigger a 14 day period in which someone else could try to form a new government.
The leader of that new administration would have to win a vote in the House of Commons to show that a majority of MPs back them.
The legislation does not specify that it must be the leader of the opposition who forms that new government. It also makes no reference to the Queen playing a role in the process.
A Lib Dem source told MailOnline: ‘To be PM Corbyn must demonstrate to the Queen that the majority of MPs support him. They do not, and will not.
‘He does not have the numbers, it’s time for him to accept this so that we can move on in order to stop the UK crashing out of the EU.’
Earlier this week, Lib Dem leader Jo Swinson repeated her assertion that her party is ready to back a government of national unity but that it cannot be led by Mr Corbyn.
She said: ‘That prime minister could be anybody that commands the confidence of the House of Commons.
‘Jeremy Corbyn doesn’t have the numbers to command a majority and until he accepts that fact he could end up being the biggest block to stopping a No Deal Brexit.’
Downing Street sources have previously suggested that Mr Johnson, pictured leaving Number 10 on October 3, would not step down even if he lost a vote of no confidence
The so-called Remain Alliance believes trying to force Mr Johnson out of Downing Street through a vote of no confidence is its option of last resort to stop a bad break from Brussels.
The alliance would likely only move forward with such an approach in the event that the PM refuses to comply with an anti-No Deal law which requires him to ask the EU for a Brexit extension if no divorce agreement has been struck by October 19.
Today the government announced its intention for the Commons to sit on October 19, a Saturday, to allow MPs to respond to the outcome of a crunch EU summit taking place on the two previous days.
That means October 19 could be the moment when MPs pull the trigger on a vote of no confidence – assuming Mr Johnson has failed to secure a deal at that summit and if he tries to dodge or frustrate the so-called Benn Act.
Should a vote of no confidence be held and Mr Johnson was to lose it, it is not immediately clear what would happen if he then refused to quit and make way for a new government.
Constitutional experts are split on whether the Queen would have the power to make him step down.
However, if a replacement PM was able to win a vote in the Commons on forming a new government it would be very difficult for Mr Johnson to try to stay in post.