UPDATE: Sleaford MP Caroline Johnson explains her backing of Boris to replace Theresa May as Tory party leader

According to the Standard's sister paper The i, Mr Johnson’s leadership bid received a double boost as a threatened criminal case against him was quashed and the party’s by-election drubbing in Peterborough prompted more MPs to back him.

Hours after the Tories came a poor third in Peterborough, the Sleaford and North Hykeham MP Caroline Johnson came out in favour of the former foreign secretary.

She said: “We can no longer faff around delaying Brexit. We’ve got to deliver it and get on with rebuilding.”

She had been among party MPs and activists, including Boris Johnson, who had been pounding the campaign trail in support of their candidate in Peterborough - to no avail - trailing behind Labour and the Brexit Party.

Mr Johnson has now been backed by 48 MPs. They believe Mr Johnson is the only contender with the ability to reach out to disaffected voters, including people attracted to Nigel Farage’s Brexit Party, and prevent a Labour government.

The Sleaford MP further explained her reasons for backing Mr Johnson, saying: "I have to agree with many of my constituents that the machinations in Parliament on Brexit have distracted attention from much of what we are doing in government.

"We need to be honest with our Members and voters, and admit that the Conservative Party is not just in trouble; it is in great danger. We could argue for hours about why this state of affairs has come about, but the essence of it is our failure to keep the promises we made on Brexit.

"Why we failed and who is to blame has been, and will continue to be, debated ad nauseam; but to the voting public it doesn’t matter, because others promise to succeed where we failed.

"The risk is not just to the Conservative Party, or even to Brexit, but to the country as a whole. If we fail to leave the EU, the country could sleepwalk into the very real dangers of a Corbyn Government," she said.

"Most fundamentally, by not delivering Brexit we erode the very core of democracy: trust between the electorate and their elected representatives.

"But we have an opportunity, a chance, to restore confidence in our Party and in our democracy. That opportunity is to elect a new leader with the drive and vision to deliver Brexit in this Parliament.

"I have consulted widely with my local party members, and within my constituency generally, and the feedback is clear:-

"We need a leader who can hit the ground running. We have a plethora of talented people who have the qualities to lead us, but we don’t have time to test them. We must pick a leader with proven abilities to lead, to inspire, and to get things done.

"We need a leader who is committed to Brexit. For far too long we have projected an image that our approach to Brexit has been one of damage limitation, and this must change. This means we must choose a leader who was committed to Brexit before the referendum. Some contenders have expressed their Damascene conversions or their commitment to deliver because of their deeply held belief in democracy but, however well motivated they are, the public may not have confidence in them.

"We need a leader who is optimistic. We need a leader who recognises the opportunities Brexit offers and is determined to realise them. For nearly three years we have been bombarded with “project fear” and it is time for “project opportunity”. We need a leader who will develop this.

"We need a leader who can communicate. Our opponents are not just the Labour and Liberal Democrat parties but also the Brexit Party. Our leader needs to be able to stand toe to toe with Corbyn and Farage and demonstrate that the Conservative Party is the only party able to deliver the Brexit we voted for and a great future for all our citizens.

"And finally, we need a leader who is brave and democratic. The people of this country voted clearly to leave the European Union. Unfortunately, there are many MPs who appear to me to feel they have some sort of Parliamentary divine right to overrule them. Our new leader must navigate the difficulties in Parliamentary arithmetic to deliver.

"In short, before we can progress with an ambitious domestic agenda we need to deliver Brexit. To do this, we need a seasoned leader who is committed to delivering Brexit and who can overcome the challenges from doubters, inspire our electorate, and lead us out of the European Union.

"I helped to support Boris Johnson’s first campaign to become Mayor of London and I have seen at first hand his charisma, his ability to engage and enthuse people, and his ability to deliver. Like the vast majority of those of my constituents who chose to tell me, I am convinced that Boris Johnson is the person we need, and I have given him my support."

The former foreign secretary was facing a private prosecution for misconduct in public office over claims during the Brexit referendum campaign that Britain pays £350m a week to the European Union. He had been instructed to appear at Westminster magistrates’ court, but the summons was quashed in a hearing at the High Court.

His lawyers argued that the prosecution – which was financed by a crowdfunding campaign – was a “politically driven process”.

Mr Johnson’s closest rival for the leadership, the Environment Secretary Michael Gove, has 32 endorsements, with the Foreign Secretary Jeremy Hunt close behind on 29.

Dominic Raab has 25 backers and the Home Secretary, Sajid Javid, 19.