Sunak's plan to impose some of the world's strictest anti-smoking rules has angered some members of his governing Conservative Party, including former prime ministers Liz Truss and Boris Johnson, who say the state should not interfere in how people live their lives.
The bill passed a vote in Britain's parliament with 383 in favour and 67 against, meaning it will progress to the next stage in parliament, where it can be subject to amendment.
Lawmakers were given a so-called free vote on the bill, meaning they did not have to vote along party lines. A similar law in New Zealand was scrapped this year by the new coalition government before the legislation went into force.
But 57 Conservatives, including Business and Trade Secretary Kemi Badenoch, voted against the plan, and the scale of the rebellion was another blow for Sunak, who has already faced criticism in his party over issues ranging from climate change to defence policy.
The legislation is one of Sunak's flagship policies before an election later this year which opinion polls suggest the opposition Labour Party will win.
The Tobacco and Vapes Bill aims to prevent children born since 2009 from ever being able to legally buy tobacco, rather than criminalising the habit.
Sunak has said it will tackle "the single biggest entirely preventable cause of ill-health, disability and death".
PUBLIC SUPPORT
About 6.4 million people were smokers in the UK in 2022, the Office for National Statistics has estimated, around 13% of the adult population.
That is much lower than other European countries such as Italy, Germany and France, where between 18%-23% of adults smoke, according to OECD figures.
There is strong support for the ban from medical and healthcare experts and charities, who say smoking causes 80,000 deaths every year plus many more smoking-related illnesses.
Polling by YouGov also suggests a smoking ban is popular, with a third of voters supporting the phased approach, 30% supporting a ban for everyone at the same time and only a quarter saying there shouldn't be any ban.
The plans have hit the share price of companies like L&B cigarette maker Imperial Brands, which has highlighted the UK as one of its key markets.
It and other tobacco companies like Dunhill maker British American Tobacco have criticised the proposed ban, saying it could fuel black market trade and will be difficult to enforce.
Business minister Badenoch said she was not a smoker and agreed with Sunak's intentions, but said she opposed the bill as she was concerned about its impact on people's rights and difficulty in enforcing the policy.
"We should not treat legally competent adults differently in this way, where people born a day apart will have permanently different rights," she said on social media platform X.
