The King’s Speech at the state opening of Parliament last month promised to reintroduce the legislation to increase progressively the age at which people can buy cigarettes.

The Sun said secret Whitehall papers confirmed the plan to extend the indoor smoking ban despite some opposition within government.

The Department of Health and Social Care said it did not comment on leaks but was considering a range of measures to “finally make Britain smoke-free”.

A spokesperson said: “We do not comment on leaks. Smoking claims 80,000 lives a year, puts huge pressure on our NHS, and costs taxpayers billions.

“We are determined to protect children and non-smokers from the harms of second-hand smoking.

“We’re considering a range of measures to finally make Britain smoke-free.”