Conservative MP Steve Baker used the vivid imagery of a "dagger in the heart" in a bid to end his party's vicious civil war over the EU referendum. The Brexit campaigner issued the plea after Lord Michael Heseltine said Boris Johnson's judgment "seemed to be going" after the former Mayor of London compared the EU's aims to Nazi leader Adolf Hitler's.

Baker, who co-founded the Conservatives for Britain group, claimed remain campaigners had resorted to personal attacks because they were losing the EU referendum debate.

He urged the pro-EU Tories to drop the ad hominem attacks so the party can come back together after the 23 June vote.

"They can't make an honest and positive case for the supremacy of EU law, EU citizenship and trade policy and all of the rest because they know it's a losing argument. We've been reduced to fear, uncertainty and doubt on the remain side," Baker told BBC Radio 4's Today programme.

He added: "Please don't anyone, on any side, follow a scorched earth policy because I spent nine months building Conservatives for Britain, making sure everybody remained on good terms and that cannot be put at risk.

"What essentially I'm saying is Queensberry Rules: so a full-frontal assault with due warning is fine, but the dagger in the heart inserted from the back through whispering in dark corridors is not OK."

However, Baker faced a hypocrisy claim because he accused fellow Conservative and Europe minister David Lidington of "polishing poo" when debating the government's renegotiation deal with Brussels in February.

"This in-at-all-costs deal looks funny, it smells funny, it might be superficially shinny on the outside, but poke it and it's soft in the middle. Will my right honourable friend admit to the house that he has been reduced to polishing poo?" the Wycombe MP declared. Baker defended the comments by claiming "I knew it would be amusing".

A Downing Street spokesperson told the BBC that "all our arguments are rooted in the thought that we are stronger, safer and better off in the EU".

David Cameron, Boris Johnson
David Cameron and Boris Johnson Getty