Tory party tensions escalate amid talk of calls for PM to step down

Prime Minister David Cameron and newly elected Labour mayor of London Sadiq Khan have said they will work together to ensure the UK votes to remain in the European Union.

Speaking at the launch of the Vote Remain battle bus at Roehampton University in London, Cameron hit back at the Leave campaign by saying it would be "some conspiracy" for the Tory son of stockbroker and the Labour son of a bus driver to join forces over the EU.

He said: "We say [vote remain], not because it's part of some massive establishment conspiracy... because we say this matters so much for this country".

"We love our country. We want our country to be the best it possibly can", he added.

Sadiq Khan echoed Mr Cameron's statements and dismissed criticism of their surprising partnership by stating he would work closely with the Tory government "where it is in Londoners' interests".

"There are many things upon which the Prime Minister and I will disagree, but what's really important... is the Mayor of London and the Government to work closely together", he said.

"We are both on the side of London, we are both on the side of the United Kingdom. I want that spirit of unity of purpose to be with us today."

Voters are fed up with critics of the Prime Minister turning the EU referendum campaign into a "kind of leadership bid", says Ken Clarke.

The former Justice Secretary suggested that pro-Leave campaigners were more interested in ousting David Cameron than contributing to an informed debate about EU membership.

Mr Clarke spoke following a weekend of upheaval in which backbench MPs called Mr Cameron "corrosive" and a "liar" as they planned to topple him even if Remain wins the referendum.

Mr Clarke called for an end to Tory in-fighting on Radio 4's Today programme: "The public are getting fed up with Tory civil wars when they thought they were being asked about the future of this country for their children and grandchildren.

"All this stuff about whether one or two backbenchers have signed letters calling for David Cameron to resign, I think most of the public would agree, is a bit of a diversion."

Prime Minister David Cameron and newly elected London Mayor Sadiq Khan are set to join forces for the first time today as they put on a united front as part of the EU Remain campaign.

It comes just weeks after Labour MPs accused the PM of being a "racist" for his personalised attacks on the winner of the race for City Hall.

The pair will jointly launch the Britain Stronger In Europe battle bus as well as a guarantee card - outlining five key pledges voters can expect to be adhered to should the country choose to stay in the EU - as part of a drive to get voters to opt to 'Remain'.

A leading advocate for Britain leaving the EU has condemned the use of personal attacks on David Cameron by the Brexit camp saying it has been a "mistake" to question the PM's integrity.

Frank Field, a former Labour minister, told BBC Radio Four's Westminster Hour: "The first mistake I think our side has made has been to question the Prime Minister's integrity. I think it's a mistake to put your sticky fingers into people's souls and say they're debasing public life.

"I think it would be very good for our Out campaign to actually concentrate on issues and not on the integrity of the other side."

It came as Cameron came under fire from Conservative colleagues with senior Vote Leave campaigners branding him "corrosive".

Conservatives Leave campaigners have been lining up to criticise Prime Minister David Cameron this weekend over immigration and his views on Britain remaining in the EU.

Labour's Alan Johnson, campaigning for the Remain camp, called the Conservative infighting "very ugly".

ITV News political correspondent Lewis Vaughn Jones reports.

Conservative MP and Leave campaigner Nadine Dorries has said Prime Minister David Cameron will be "toast within days", depending on the result of the European referendum.

Speaking to Robert Peston on ITV's Peston on Sunday, she said her "letter is already in", along with 50 other MPs, asking for the Prime Minster to stand aside.

She said "David Cameron might just survive if there's a 60/40 majority to Remain" but warns anything less should see the end of his leadership.

"He has lied, profoundly. There are many issues at which David Cameron has told outright lies and the trust, because of that, has gone from both him and George Osborne", Dorries said.

She added: "I always have backed the only politician in Westminster who has a proven track record of achievement, and that's Boris Johnson".

Newly elected London mayor Sadiq Khan has criticised both EU Leave and Remain campaigns for "talking nonsense".

Speaking to Robert Peston on ITV's Peston on Sunday, Mr Khan said the public should hear a "positive and patriotic case" instead of "too much project fear".

He said: "One side is saying if we remain in the European Union, it's the end of time. The other side is saying if we leave the European Union it's the end of the world as you know it".

Khan added there's a "patriotic case for our city's interest to remain in the EU" and said London has always been "open-minded, outward-looking [and] embracing cultures".

Meanwhile the London mayor has defended criticism after agreeing to spend Monday on the Remain campaign trail alongside Prime Minister David Cameron - apparently against the wishes of Labour leader Jeremy Corbyn.

"We're never going to be best friends... I'm willing for us to put aside our differences, put aside the grudges that he or I may have, but this debate is far more important than David Cameron or me", he added.

Brexit campaigner Dr Liam Fox has said that if Britain votes to leave the European Union "the best thing" would be for David Cameron to stay on as prime minister.

Speaking to the BBC's Andrew Marr show, the former defence secretary said: "We will need to have a government position before we enter into negotiations under article 50.

"We need a period of stability and whatever our views have been during the referendum, we need to put to bed all those personal views and understand that stability for the country is the most important element."

It comes as Conservative MP Andrew Bridgen criticised Mr Cameron, insisting he is "finished" as Tory leader because of the way his "Operation Fear" tactics have divided the party.

• Read: Gove and Johnson warn PM's credibility on the line over EU