Shadow Chancellor Sir Mel Stride has launched a scathing attack on Nigel Farage’s Reform UK, accusing the party of peddling “fantasy economics” as he warned that its policies would be “extremely dangerous and very damaging to our economy.”

Speaking this week Sir Mel said theConservatives must “shine the light of truth on Reform and expose the fantasy economics that they peddle.”

He added: “Our role is to shine the light of truth on Reform and expose the fantasy economics that they peddle, the ideas that don't add up; that sound great, but don't add up.

“You could start by saying they deal in fantasy economics […] You can then work your way into a discussion about why it's important that parties don't peddle that kind of policy agenda and start to deconstruct in a thoughtful way some of the things that they say.

“Reform might say, we're going to take everybody earning up to £20,000 out of Income Tax altogether. Thoughtfully, we should observe that that would cost about up to £80 billion … Reform has a duty to explain how it's going to fund that. Otherwise, it's left peddling fantasy demands that would be extremely dangerous and very damaging to our economy; and that would have real consequences.”

Asked if the Conservatives should ever work with Reform, Sir Mel ruled it out saying: “I don't want to have any coalition or arrangement with Reform. Why would I want to have a coalition, or something about a merger, or whatever it may be, with a party whose economic prescription for our country will be completely ruinous?”

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He also warned against “populist politics” and said the Conservatives must present themselves as “the grown-ups in the room.”

“I don't think we should be indulging in populist politics in the sense of going out there and promising stuff that we know people want to hear but we don't have any proper plans for,” he said. “We have to emerge, if we are to win the next election, as the grown-ups in the room that have done the deep thinking to come up with the answers to meet the challenges that we face.”

Stride said thoughtful conservatism would eventually “triumph” over populism: “We have to fight harder for the kind of things that I think are important, including thoughtful, deep debate, rather than populist, apparent solutions.”

On the next election, he urged calm about polling volatility. “WhatNigel Farage has got to do is keep spinning all those plates and letting off all those fireworks for another four years. That is a very long time. Anybody who predicts that Reform is going to win the next election – or we're not going to win the next election – four years out … needs to think again.”

He made the remarks in the first interview published by the new online magazine Centre Write, launched this week by the centre-right think tank Bright Blue.

Bright Blue, which describes itself as “the independent think tank for defending and improving liberal society,” this week launched Centre Write, an online magazine publishing daily commentary, interviews, and debates across politics, policy, philosophy and culture.

Contributors will include Nicholas Boys-Smith of Create Streets, Adam Smith Institute president Madsen Pirie, Telegraph columnist Andrew Lilico, and former GB News presenter Albie Amankona.

Reform UK was approached for comment.