Kemi Badenoch has become the first Cabinet minister to reveal she will not back Rishi Sunak’s proposal to ban young people from ever smoking, in a blow to the Prime Minister’s authority.

The Business Secretary said she will vote against the Tobacco and Vapes Bill, with the legislation facing its first parliamentary hurdle on Tuesday night.

The Bill would make it illegal to sell tobacco products to anyone born after January 1 2009, which covers children who are currently 15 or younger, but does not criminalise current smokers.

The Prime Minister has given Conservative MPs a free vote on the Bill, meaning they will not be punished if they do not support the Government’s position.

But Ms Badenoch and other high-profile Tories’ dissent highlights discontent with Mr Sunak’s leadership and posturing for the leadership as his party languishes in the polls ahead of the upcoming general election.

Labour will back the proposals, meaning they are likely to move forward on the journey to become law.

Before the Commons vote, Ms Badenoch wrote on X, formerly Twitter: “I have significant concerns and appreciate the PM making this a free vote. It gives me the opportunity to express my personal view, outside collective responsibility.

“The principle of equality under the law is a fundamental one. It underpins many of my personal beliefs.”

Ms Badenoch, who is seen as a leadership favourite among Tory members, added: “We should not treat legally competent adults differently in this way, where people born a day apart will have permanently different rights.

“Among other reasons it will create difficulties with enforcement. This burden will fall not on the state but on private businesses.

“Smoking rates are already declining significantly in the UK and I think there is more we can do to stop children taking up the habit.

“However, I do not support the approach this Bill is taking and so will be voting against it.”

Another potential contender to run for the Tory leadership, former immigration minister Robert Jenrick, also came out against the policy.

He tweeted: “I believe in personal freedom. Let’s educate more and ban less.

“I also believe in the principle of equality under the law. A phased ban of smoking would be an affront to that. I will therefore vote against the Tobacco and Vapes Bill.”

They were joined by Foreign Office minister Anne-Marie Trevelyan, who said she hoped MPs could “make amendments which will make it law which will be more likely to actually deter young smokers without removing freedom of choice for adults”.

The intervention by serving ministers comes after several senior Tories, including former prime minister Liz Truss, said they would not back the Bill due to concerns about freedom of personal choice.

In the Commons, Ms Truss claimed the ban is the result of a “technocratic establishment” aiming to “limit people’s freedom”, and described the Bill as a “virtue-signalling piece of legislation”.

In a warning to Tory colleagues, Ms Truss said she was “disappointed” that a Conservative Government was bringing forward a smoking ban.

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Liz Truss (Victoria Jones/PA)

She claimed there were enough “finger-wagging, nannying control freaks” on the opposition benches willing to support the proposals, urging Conservatives to “stand by our principles and our ideals”.

Former Conservative Party chairman Brendan Clarke-Smith suggested the proposal could lead to further health-related bans.

He said: “What next? A ban on alcohol? A ban on takeaways? I would declare an interest in both of those. Both of these are bad for us when they are not done responsibly. But we are adults, these are our choices, these are not the state’s choice.”

Other Conservative former ministers supported the plans, with ex-health secretary Sir Sajid Javid criticising colleagues for “choosing to stand up for big tobacco against the interest of their constituents”.

Steve Brine, Conservative chairman of the Health Affairs Committee, suggested small-state Tories should back the measures to eliminate costs for the taxpayer.

“If you are a Conservative and a smaller state is your thing… you should be right behind a healthier society, one that needs the state less, one that relies on the state less, one that costs the state less,” he said.

Health Secretary Victoria Atkins said she understood colleagues’ concerns about freedom of choice, and conceded Conservatives were “not in the habit of banning things”, but warned the Commons there was “no liberty in addiction”.

“Nicotine robs people of their freedom to choose. The vast majority of smokers start when they are young, and three-quarters say that if they could turn back the clock they would not have started,” she added.

Shadow health secretary Wes Streeting confirmed Labour is giving “wholehearted” support to the Bill.

He added that his party is “only too happy to defend the Health Secretary against the siren voices of big tobacco” gathered on the Tory benches.