The tobacco industry has criticised the proposals to ban younger generations from ever buying cigarettes, a move that would give Britain some of the world's toughest smoking rules and hurt the sales of major tobacco firms.
The Tobacco Manufacturers Association said they were a "disproportionate attack" on adults' rights and would fuel black market trade.
"The prohibition of legal products always has dangerous side effects and opens the door to criminal gangs to sell illegal products," it said.
Imperial Brands, which makes Winston cigarettes and Golden Virginia rolling tobacco, also warned the ban threatened "unintended consequences".
British American Tobacco said the proposals would be difficult to enforce, and risked creating a new category of "under-age adults".
"Enforcement of existing tobacco control policies is already under-resourced. An additional ban is only going to make it more difficult to police," the maker of Lucky Strike and Dunhill cigarettes said in a statement.
According to a briefing paper, the government intends to raise the smoking age by one year every year, potentially phasing out smoking among young people almost completely as soon as 2040.
"A 14-year-old today will never legally be sold a cigarette," prime minister Rishi Sunak told the Conservative Party conference, where he announced the plan.
The policy would need to pass a free vote in the parliament. This means lawmakers can vote however they like rather than in line with party policies.
Free-market think tank Institute of Economic Affairs (IEA) said the cigarettes ban is "hideously illiberal” and “full of holes”.
“It will create a two-tier society in which adults buy cigarettes informally from slightly older adults and will inflate the black market in general,” Christopher Snowdon, head of lifestyle economics at IEA, said.
“It may well breach equalities legislation and will very likely be challenged in the courts. It will certainly create huge problems for retailers and may ultimately require a system of national ID cards."
If passed, Britain would become the first country in Europe to join New Zealand, which announced a similar plan last year, in banning smoking for future generations.
The change could hurt companies who generate a relatively large portion of their earnings from British tobacco sales, analysts said, such as Japan Tobacco, maker of Camel and Benson & Hedges, and Imperial Brands.
While short-term effects were likely minimal, over time the ban's impact "could gradually become material", said Owen Bennett, analyst at Jefferies, adding people aged 18-25 make up around 10 per cent of Britain's current adult smokers.
Shares in Imperial Brands fell 3.2 per cent to their lowest since March 2022, while shares in BAT, which has a lower exposure to the British cigarette market, were down 1.2 per cent by 1357 GMT.
A risk for all companies is that other nations follow suit, Bennett noted. Denmark is already considering a similar move, and a number of nations also have targets to reduce smoking to minimal levels in the relatively near future.
(With inputs from Reuters)
Steph McGovern
Lucy Edwards