The British government will introduce a bill in parliament to fulfil its promise to phase out smoking among young people by banning tobacco sales for future generations.

The Tobacco and Vapes Bill, if passed unamended on Wednesday, will be one of the world's toughest anti-tobacco laws and prevent children turning 15 this year or younger from ever being able to be legally sold tobacco.

The government said smoking itself would not be criminalised, therefore anyone who can legally buy tobacco now would not be prevented from doing so in future.

"If we want to build a better future for our children we need to tackle the single biggest entirely preventable cause of ill-health, disability and death: smoking," Conservative Prime Minister Rishi Sunak said in a statement.

Critics say the move is "unconservative", and former prime minister Liz Truss is one of several members of the governing party to say they will vote against the legislation.

Despite the opposition, the legislation is expected to pass with the opposition Labour Party suggesting it would support the measure.

Last month, a similar law introduced by New Zealand banning tobacco sales to those born after January 1, 2009 was repealed by the country's new coalition government.

The British government said smoking costs its National Health Service and economy an estimated 17 billion pounds ($21.63 billion) a year.

A sharp rise in vape use by non-smokers and young people has forced the British government - a proponent of vaping as a way to reduce the harms of smoking - to consider tougher controls.

Under the proposed legislation, there will also be new powers to change how vapes are displayed in shops, restrict vape flavours and packaging intentionally marketed at children to combat the rise in youth vaping.