The Speaker of the Commons has been urged to allow a vote on an inquiry into Boris Johnson ’s “consistent failure to be honest”.

Six opposition parties - not including Labour - want Sir Lindsay Hoyle to allow a motion that would refer the PM to the powerful committee on privileges.

In their letter, leaders of the SNP, Lib Dems, Greens, Plaid Cymru, SDLP and Alliance express their “deep concern” that the PM’s repeated failure to be truthful is damaging the reputation of Parliament.

They continue: “This is not a question of occasional inaccuracies or a misleading use of figures: it is a consistent failure to be honest with the facts, or to correct wrong information at the earliest opportunity when misleading information is given.

"This, we believe, amounts to a contempt of the House.”

Keir Starmer, pictured today, was the only major opposition leader who did not sign the letter
Keir Starmer, pictured today, was the only major opposition leader who did not sign the letter

Labour leader Keir Starmer was invited to sign the letter but declined.

Sources said the party does not normally sign up to 'round robin' initiatives launched by other parties.

A Labour source insisted the party had corrected the Prime Minister a number of times, including in a recent Point of Order raised by Jonathan Ashworth at the end of PMQs.

There is no realistic prospect of MPs winning a vote, given the size of the Tory majority.

But a debate on the subject would be embarrassing for the PM - and comes after the Mirror and others repeatedly highlighted his false statements.

Last summer he was rapped by the statistics watchdog after telling PMQs: "There are hundreds of thousands, I think 400,000, fewer families living in poverty now than there were in 2010."

Last month, No10 failed 19 times to correct the PM's false claim that Keir Starmer had voted against a 2.1% pay rise for nurses.

Boris Johnson has made false claims about a transport body and a pay rise for nurses
Boris Johnson has made false claims about a transport body and a pay rise for nurses

It was the third time Mr Johnson had been accused of misleading the Commons in as many weeks.

He also wrongly said there were no cuts to a northern transport body and suggested all outstanding Covid contracts had been published.

Green Party MP Caroline Lucas told the Guardian she was partly inspired by a Twitter video about the PM's "lies" by campaigner Peter Stefanovic.

“It’s hard to recall any prime minister who has treated parliament with the contempt that this one does,” she told the newspaper.

“There is a normalisation of lying to the house which is deeply dangerous, especially coming from an increasingly authoritarian government which is looking at every means to avoid accountability.”

It comes as the Tory leading a Commons investigation into lobbying said he was "confident" there was cross-party support for "meaningful change" in the wake of the Greensill capital scandal.

Tory MP William Wragg also confirmed that former PMs have indicated they would be willing to appear in front of the inquiry.

A government spokesperson told The Guardian: “The prime minister follows the ministerial code.”