Boris Johnson has branded Rishi Sunak's policies as "absolutely nuts" with a particularly furious attack on his plan to ban smoking.

The ex-PM said it was "mad" the "party of Winston Churchill wants a ban on [cigars]" as he sided with Liz Truss in opposing the anti-smoking policy. Mr Johnson has previously said the Conservatives need to "stop telling people what to do" after Mr Sunak announced his plan to raise the legal age of buying tobacco by one year every year so that a 14-year-old today will never be able to legally buy cigarettes.

Speaking at a conservative event in Canada, Mr Johnson said some of Mr Sunak's policies that are “being done in the name of conservatism” are “absolutely, absolutely nuts”. He continued: “I see my beloved party... we’re banning cigars. And what is the point? The party of Winston Churchill wants a ban. I mean, donnez-moi un break as they say in Quebec. It’s just mad.”

Health campaigners have urged Mr Sunak to resist pressure from his predecessors who are part of "a tiny minority out of touch with the public". MPs are expected to vote on the plan later this year. Deborah Arnott, chief executive of Action on Smoking and Health (ASH), told the Mirror in January that those opposing Mr Sunak’s plan are “making a lot of noise and wind but there is strong cross-party support and they’re not going to win”.

Ms Arnott said the public “overwhelmingly supports” the move. A YouGov poll carried out for the public health charity in November found 67% of people in England back the PM’s plan to raise the smoking age. Tory voters came out on top, with 74% of those who intend to vote Conservative at the next election backing it, followed by 72% of those intending to vote Labour and 65% of those intending to vote Lib Dem.

In the discussion at the Canada Strong and Free Network conference in Ottawa, Mr Johnson said he hoped the Conservatives, who are trailing behind Labour in the polls, could “turn things around in the next few months”. He also urged the PM to increase defence spending. “Now is the moment for an even more robust posture," he said. "We all need to recognize the world is more uncertain, more dangerous, we all need frankly to be spending more on defence — that goes for the U.K. as well as everybody else.”

The broadside came as a former Tory Chancellor has warned the Tories are heading for a "pasting" at the next general election. Lord Philip Hammond, who was Chancellor during Theresa May's rocky premiership, made the gloomy forecast as mega-polls last week pointed to a worse defeat for the Tories this year than in 1997. Speaking to the BBC's Today Podcast, Lord Hammond said: "I can easily envisage - and the polls are certainly suggesting - the Conservative Party will take a pasting at the next election."