Boris Johnson has hailed a “significant milestone” as the number of people in the UK receiving a coronavirus vaccine passed 15 million.

The Prime Minister said it was an “extraordinary feat” just over two months after 91-year-old Margaret Keenan became the first person in the world to receive a Covid-19 jab as part of a mass vaccination programme.

It puts the Government firmly on course to meet it target of offering a first dose to everyone in the the UK in its top four priority groups – including all over-70s – by Monday.

In a video message posted on Twitter, Mr Johnson confirmed it had already been passed in England, while on Friday First Minister Mark Drakeford said it had been reached in Wales.

The Prime Minister said: “Today we have reached a significant milestone in the United Kingdom’s national vaccination programme.

“This country has achieved an extraordinary feat – administering a total of 15 million jabs into the arms of some of the most vulnerable people in the country.”

The announcement paves the way for the rollout to be extended to the next five groups – including the over-50s – who are due to be completed by the end of April.

In England, 1.2 million letters have already gone out to 65 to 69 year-olds and the clinically vulnerable inviting them to book an appointment.

The news will also intensify the pressure on ministers to begin easing lockdown restrictions and re-opening the economy.

Earlier, Foreign Secretary Dominic Raab rejected an “arbitrary” demand by lockdown-sceptic Tories in the Covid Research Group to commit to lifting all legal restrictions in England by the end of April.

Ministers will now begin their review of the restrictions ahead of an announcement by Mr Johnson on February 22 setting out his “roadmap” out of lockdown.

More than 60 MPs in the CRG are backing a letter to the Prime Minister insisting he commit to a firm timetable for ending controls.

They said schools “must” return on March 8 as planned with pubs and restaurants opening in a “commercially viable manner” from Easter, with the end of April marking the final end of lockdown.

Mr Raab, however, said that, while ministers wanted to lift controls as quickly as possible, it was essential to ensure the disease was under control first.

“We do need to be very careful how we proceed.

“We have made good progress.

“We don’t want to see that unravel because we go too far too quick,” he told Sky News’s Sophy Ridge On Sunday programme.

“We are not making what feels to me like a slightly arbitrary commitment without reviewing the impact that measures have had on the transmission and the hospital admissions of the virus.

“We need to retain some flexibility to deal with the variants, which of course are part and parcel of dealing with the pandemic but do alter the precise timeframe.”

The CRG chairman Mark Harper, however, insisted their demands represented a “sensible” way forward as more people were protected by the vaccine.

“They’re not random, arbitrary timetables.

“It’s linked very much to the rollout of the vaccine,” he told Times Radio.

“Once you have vaccinated the top nine groups who represent 99% of the people who have sadly died from Covid and about 80% of those who are seriously ill, I don’t think there is a justification for all of these draconian restrictions.”

Mr Raab said they still aimed to start reopening schools on March 8 although he would not be drawn on whether they would all be able go back at the same time amid reports that secondary schools could return a week later.

“We need to wait to evaluate the data carefully and allow those plans to be put in place,” he said.

“Because we are making progress I think we can be confident we will be able to start that process.”

The Foreign Secretary indicated allowing people to socialise outdoors and the reopening of non-essential shops would also be early priorities as controls eased.

Meanwhile in Wales, where schools are due to begin re-opening to some pupils on February 22, Mr Drakeford warned they could close again if there was a resurgence of the disease.

“The advice to us from our chief medical officer and scientists is that you should, in these early stages, always take measures that could be reversed quickly if you needed to do that,” he told Sky News.

“If there were to be unintended consequences of having three to seven-year-olds back into school, then, of course, we would be able to go into reverse.”

Despite the hopes among ministers that they will be able to begin a significant easing in England, scientists continue to warn that they could face another wave of the pandemic as bad as the current one if they go too fast.

During a visit to a vaccine manufacturing facility in Teesside on Saturday, Mr Johnson said that while he was “optimistic” about the prospects they would have to study the data “very, very hard” as he did not want to be forced into a “reverse ferret”.