Kemi Badenoch has announced she is opposing Rishi Sunak’s smoking ban because it will mean “people born a day apart will have permanently different rights”. In a blow to the prime minister’s authority, Badenoch published a statement before the vote saying she had “significant concerns” about the legislation. Badenoch, the business secretary, who is seen as a potential Conservative leadership challenger, said she agreed with Sunak’s intentions but that “the principle of equality under the law is a fundamental one”. Her statement signalled her decision to wavering Conservative MPs before the first Commons vote on the the prime minister’s tobacco and vapes bill on Tuesday evening. It could encourage more Tory MPs, several of whom have already spoken up against it, to oppose the ban. Conservative MPs have been given a free vote. Badenoch wrote on X: “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.” Penny Mordaunt, another cabinet minister and potential Conservative leadership challenger, is among those wavering over whether to support the ban. The Foreign Office minister Anne-Marie Trevelyan has also said she will oppose the proposed ban. Mordaunt, the leader of the House of Commons, is known to have reservations about bill and the precedent it would set for banning other unhealthy practices. The legislation would ban smoking for future generations by making it illegal for anyone born in 2009 or later to buy tobacco products in the UK. Mordaunt’s position appears to mirror criticism from other Conservative figures who attacked the bill on Tuesday, which is having its second reading in the Commons. MPs will hold their first vote on it before a final one expected in June. The former prime minister Liz Truss blamed “unelected individuals” in the Department of Health and Social Care for the government’s planned smoking ban as she launched an apparent attack on civil servants such as the chief medical officer for England, Prof Chris Whitty. She also claimed Thérèse Coffey, her friend and health secretary in Ther short-lived government, had put the plans “in the bin” but that they had “re-emerged like a bad penny”. Truss launched her attack in an interview with the BBC as hostilities opened among Conservative MPs before the second reading of the bill on Tuesday, with another former minister rejecting her claim that the plans were “unconservative”. “What I think about this smoking ban is that it’s something that the Department of Health … ie unelected individuals … have been pursuing for some time,” Truss told the BBC’s political editor, Chris Mason, in one of the latest in a series of interviews to promote her new book. Truss, who has limited support among Tory MPs after her disastrous period in Downing Street but is one of the leaders of the rebellion against the bill, claimed she was worried about where the proposals would lead, suggesting people could end up with a “sugar allowance”. The bill is important to Sunak as a legacy achievement of his time in Downing Street. Opposition by Mordaunt – regarded as a leadership candidate of the centre – could leverage her more traditional Conservative credentials among Tory grassroots and MPs from the party’s libertarian wing. Before she became an MP in 2010, Mordaunt was a director at Media Intelligence Partners (MIP), a communications company. After she resigned from the firm it was involved in working for the tobacco firm Philip Morris International as it campaigned against the coalition government’s plain packaging plans for cigarettes. Truss in her attack did not name Whitty, who used an article in the Guardian on Tuesday to say that lobbying by big tobacco “needs to be addressed head on”, as email evidence emerged of campaigning tactics to put pressure on MPs to sink Rishi Sunak’s smoking ban bill. Another former minister, Jesse Norman, aimed a broadside at colleagues in his own party on Tuesday, saying on X: “Very hard to see what is supposed to be unconservative about the tobacco and vaping bill. It’s a gradual long-term reform that doesn’t affect anyone now smoking, protects young people from a dangerous addictive drug, supports the NHS and saves the taxpayer and society a fortune.” Simon Clarke, a former minister and one of the Tory MPs opposing the bill, claimed the government’s generational smoking ban risked making the habit “cooler” and that it was a “slippery slope” to bans on alcohol and fast food. “There are good ways to tackle a problem like this and then there are bad ways, and I think that an outright ban risks being counterproductive. I think it actually risks making smoking cooler, it certainly risks creating a black market, and it also risks creating a unmanageable challenge for the authorities,” he told BBC Radio 4’s Today programme. Clarke said education and the tax system should be used as tools to deter people from smoking. Asked about opinion polls that showed two-thirds of people in Britain backed a phased smoking ban – a figure that extends to 70% among those who voted Conservative in 2019, Clarke said: “There are some things, of course, which are not necessarily philosophically or practically right that would command support in the opinion polls.”