The prime minister will hold a Downing Street coronavirus news conference later, Number 10 has said.
Boris Johnson is expected to discuss the spread of the Indian COVID-19 variant - and the steps the government is taking to combat it - when he addresses the nation at 5:30pm alongside England's chief medical officer Professor Chris Whitty.
Downing Street has insisted that England's roadmap out of lockdown, with the next easing of restrictions taking place on Monday, remains on track.
Latest figures show there are 1,313 cases of the variant in the UK, up from the 520 recorded the previous week.
Government data also shows that four people have died in the UK after being infected with it, the first known domestic deaths from the new variant.
The Department of Health said there is "no firm evidence yet to show this variant has any greater impact on severity of disease or evades the vaccine".
But the PM said earlier this week that the UK was "anxious" about the variant and the government was "ruling nothing out" when it comes to tackling its spread.
The government is now considering bringing forward vaccine second doses in areas with high numbers of cases of the variant.
The Department of Health said "most cases are in the North West of England, with some in London".
Surge testing, increased genomic sequencing and enhanced contact tracing have all been introduced in the 15 affected areas.
Mobile testing units have been deployed in Bolton, with door-to-door PCR COVID testing being offered to 22,000 residents and a rapid response team of 100 nurses, public health advisers and environmental health officers deployed.
Surge testing is in place in Sefton, Merseyside, with anyone over 16 who lives, works or studies there urged to take a PCR test.
Measures have also been introduced in other parts of the country, including in areas of London.
Despite this, Mr Johnson has said at this stage there is no reason to delay England's roadmap out of lockdown.
From 17 May, pubs and restaurants will be able to reopen indoors and people will be allowed to mix indoors as two households or under the rule of six.
People will also have the choice whether to socially distance with close family and friends they meet up with.
On 21 June, step four, the government wants to end "all limits on social contact".
Vaccines minister Nadhim Zahawi told Sky News earlier that the roadmap for Monday "remains in place because the vaccines are delivering".
"At the moment we have no evidence that it escapes the vaccines or is more severe in its impact on people," he said.
This was reiterated by the PM's spokesman later on Friday.
"We've announced the changes that are taking place on Monday and the prime minister said yesterday himself he expects they will go ahead," he said.
"The prime minister himself has said that at the moment we don't see any evidence or data to suggest we're not on course for the timings in the road map."
The spokesman said that once step three has been taken, the government will "continue to monitor the data closely" ahead of the next easing on 21 June.
Mark Harper, chairman of the COVID Recovery Group of Conservatives MPs, urged ministers to stick the roadmap.
In a tweet ahead of Mr Johnson's news conference, the MP said: "Ministers need to keep cool heads and be driven by the evidence of our vaccines' efficacy & avoid sacrificing the progress made by our rollout."