TORY MPs vying to become the next prime minister have come under fire for uncosted “fantasy tax cuts” in a bid to appeal to Conservative activists.

Foreign Secretary Liz Truss has thrown her hat into the ring to replace Boris Johnson with a pledge to start cutting taxes “from day one”.

But the race to become the next Tory leader, and prime minister, has seen multiple MPs among the contenders make a series of uncosted promises.

Priti Patel is also set to launch her leadership bid after reportedly meeting with pro-Brexit Tory MPs, hitting out at “fashionable” tax cuts being floated by her rivals.

Robert Jenrick, a former Cabinet minister who is backing former chancellor Rishi Sunak, criticised rivals for pledging unachievable tax cuts at a time when the party’s “credibility” is under strain.

He added that “announcing fantasy tax cuts to help get through a leadership election” would be an “unwise” move.

Under the tagline “Trusted to deliver”, Ms Truss kicked off her campaign with a video highlighting her work on trade deals and the controversial Northern Ireland Protocol Bill.

Ms Truss said a prime minister with “experience, who can hit the ground running from day one” is needed, in a possible dig at her rivals without Cabinet experience.

She told the Daily Telegraph she would “start cutting taxes from day one”, and would cut the National Insurance hike introduced in April, mirroring a pledge of rival Sajid Javid.

Sajid Javid, who kickstarted the revolt against the Prime Minister when he resigned as UK health secretary, insisted that he had always been “transparent” with the tax authorities.

In a campaign launch, Mr Javid revealed plans to woo Tory colleagues and grassroots activists with a promise of tax cuts and an ambitious house-building programme as he said that Conservatives were facing a “wake up and smell the coffee” moment.

But questions about his former tax arrangements overshadowed part of the launch, with Mr Javid declining repeatedly to get into specifics about where he has previously paid tax.

He said: “I believe I’ve been open and transparent about this. I’ve set out before this campaign that, because… before politics my job was an international job, I travelled a lot.

“I lived in the (United) States, I lived in the UK, I lived in Singapore, I was tax resident in different countries, as part of my job, it had an impact on my statuses. That’s not unusual.

“I had a tax adviser, accountants that would help me with my international taxes, I moved around a lot.

“And the test for me was to make sure that whatever you do, when it comes to your taxes, your personal tax affairs, that is always correct, proper, within all the rules, and that was met at all times.

“So I am perfectly happy about that. And I am certain that I’ve never had an issue with HMRC. I’ve never had a tax investigation. I’ve always been transparent, fully transparent, with the tax authorities.”

UK Transport Secretary Grant Shapps released a video appealing to the Tory MPs who will whittle down the candidates by touting his experience as a campaigner.

With Conservatives nervous of losing their jobs after Mr Johnson led the party to dire recent electoral performance, Mr Shapps told MPs: “I can help you win your seat.”

Tom Tugendhat, chairman of the Commons Foreign Affairs Committee, who has never been a minister, pledged to cut taxes on jobs and fuel and painted his candidacy as a “clean start”.

Jeremy Hunt, who has been both health and foreign secretary, expressed a desire to “cut all taxes” in an interview with BBC Breakfast.

Chancellor Nadhim Zahawi has claimed he was being “smeared” over his tax affairs, and reiterated a pledge to publish his returns annually if he enters No 10.

“I was clearly being smeared. I was told that the Serious Fraud Office, the National Crime Agency, HMRC, were looking into me,” he told Sky News.

“I’m not aware of this. I’ve always declared my taxes – I’ve paid my taxes in the UK.”

Mr Zahawi said he would “look at what the options are in terms of backdating and publishing annually”, but added he would not release his tax returns from over the past decade.

“If I am prime minister, I will publish them going forward,” he added.

“I don’t think being retrospective is right. I was in business before, I came out of that, of course, now I’m in politics.”

Attorney General Suella Braverman pledged to amend the Northern Ireland Protocol Bill to set VAT, excise and the regulation of medicines directly under UK law from day one.

She has also pledged a move to remove new EU laws from applying to Northern Ireland, risking further souring relations with the bloc.