Sir David King, a former chief scientific adviser to the government, said the current COVID-19 figures are “evidence of another wave appearing”.

He told Sky News: “[There are] 5,300 new cases of the disease per day in the United Kingdom and we’re up about 2,000 on last week.

“Now we’ve been discussing whether or not we’re going into a serious third wave and I don’t think we can possibly wait any longer.

“This is the evidence of another wave appearing.”

Around 400 infections a day are among people who have had both vaccines, said Sir David, who is the chair of the Independent Sage Group.

He said: “We know that anyone vaccinated twice is relatively safe against the virus.

“But let’s not forget the one in 25 new cases are people who have been vaccinated twice – that means 400 new cases a day are people who had the vaccine twice.”

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He also called on ministers to delay the proposed 21 June easing of lockdown in England.

“[On] the number of people in our hospitals, which the government says is relatively stable, it’s 932 per day going into hospital, which is up 65 from last week. It’s not actually stable, it is slowly rising,” he said.

“What all of this means is that intensive care is needed for a significant proportion of our population today.

“I’m very reluctant to say that we should not go out of lockdown on June 21, but I think the figures are in now, and it will be wise for the government to announce right away a delay in opening, just so that we can all plan for the post June 21 period.”

When asked for how long, he replied: “I would give a few weeks’ delay and see how the fingers are emerging.

“So, I don’t know how long.

“As the prime minister has said, it’s data, not dates, that we should be governed by, and that’s response as well.”