Boris Johnson looks set to delay the final lifting of coronavirus lockdown restrictions in England following another sharp rise in cases of the Delta variant.

Ministers are considering putting back the relaxing of controls planned for June 21 for up to four weeks as they race to roll out the vaccine to younger age groups.

A final decision is expected to be taken on Sunday ahead of a formal announcement by the Prime Minister at a news conference the following day.

It comes amid repeated warnings from some scientists that the rapid spread of the Delta variant first identified in India could lead to a “substantial” third wave if controls are lifted.

Doctors leaders in the British Medical Association (BMA) joined calls on Friday for the final lifting to be put on hold to enable millions more to gain the protection of the vaccine.

BMA council chairman Dr Chaand Nagpaul said: “With only 54.2% of the adult population currently fully vaccinated and many younger people not yet eligible, there is a huge risk that prematurely relaxing all restrictions will undo the excellent work of the vaccine programme and lead to a surge of infections.

“It’s not just about the number of hospitalisations, but also the risk to the health of large numbers of younger people, who can suffer long-term symptoms affecting their lives and ability to work.”

However a delay – potentially to July 19 – will come as a bitter blow to many businesses, particularly in the hospitality and leisure sectors, which had been pinning their hopes on a full summer reopening to help recoup some of the losses of the past year.

For Labour, shadow home secretary Nick Thomas-Symonds said the country was now paying the price for the refusal of ministers to heed the warnings of its own Scientific Advisory Group for Emergencies (Sage).

“Any delay in rolling back restrictions would be a huge blow for many families and businesses across the country. The fault for this lies squarely with Conservative ministers,” he said.

“Despite warnings from Labour, Sage and others they continued with a reckless border policy that allowed the Delta variant to reach the UK and spread.

“Now the British people look set to have to pay the price.”

Scientists now estimate that 96% of all new cases of coronavirus are attributed to the Delta variant.

The latest figures from Public Health England (PHE) showed there have been 42,323 cases of the Delta variant confirmed in the UK, up by 29,892 from the previous week.

It estimates the strain is 60% more transmissible compared with the previously dominant Alpha, or Kent, variant, and that cases are doubling every four-and-a-half days in some parts of England.

Meanwhile, Merton Council in south London has announced that it is stepping up targeted surge testing in two areas – including an industrial estate in New Malden – where there have been recent outbreaks.

Additional testing is also being carried out in Staffordshire and in Northwich and Winsford in Cheshire.

The setback comes as leading figures behind the successful vaccination programme were recognised in the Queen’s Birthday Honours List.

They include the Oxford/AstraZeneca vaccine mastermind Professor Sarah Gilbert and the ex-chairwoman of the UK vaccine taskforce Kate Bingham who are both recognised with damehoods.