Ministers are poised to order further action in response to the spread of the Indian coronavirus variant of concern.
It comes after new figures showed cases of the strain have more than doubled in a week.
Data from Public Health England (PHE) shows a rise in cases from 520 to 1,313 this week in the UK. The agency saying cases were “rising in the community” and it was assessing the impact and severity of the variant.
One response being considered is bringing forward the date for a second dose of vaccine for eligible groups to increase protection.
Health Secretary Matt Hancock said the situation was being monitored carefully and the Government “will not hesitate to take further action if necessary”.
Prime Minister Boris Johnson has not ruled out local lockdowns being necessary to contain the spread of the virus.
Dr Susan Hopkins, Covid-19 strategic response director at PHE, said: “We need to act collectively and responsibly to ensure that variants do not impact on the progress we have all made to drive down levels of Covid-19 and the increased freedom that brings.”
In Bolton, which has one of the highest case rates of the variant in the country, mobile testing units have been deployed and door-to-door PCR Covid testing has been offered to 22,000 residents.
A vaccine bus has been set up to increase uptake among those who are eligible and a rapid response team of 100 nurses, public health advisers and environmental health officers has been sent in.
Meanwhile, surge testing has been deployed in Sefton, Merseyside, after cases of the Indian variant were confirmed in the Formby area, with anyone over 16 who lives, works or studies in the area urged to take a PCR test.
Measures have also been brought in elsewhere, including in parts of London.
Mr Hancock said: “We are monitoring the situation very carefully and will not hesitate to take further action if necessary.
“It is imperative we all continue to be vigilant, and if you live in one of the 15 areas where we’ve introduced surge testing, make sure you get a free PCR test.
“And everyone who’s eligible needs to come forward and get a jab.”
Mr Johnson said the Government was “anxious” about the variant and “there is a range of things we could do, we are ruling nothing out”.
Despite the spread of the Indian variant, Mr Johnson said there was “nothing that dissuades me” from easing England’s lockdown on Monday or the further steps towards normality on June 21.
But he added “there may be things we have to do locally and we will not hesitate to do them if that is the advice we get”.
Local lockdowns are only expected to be used if evidence suggests they are necessary to contain or suppress a variant which escapes the vaccine.
Although the Indian variant is thought to be highly transmissible, vaccines are expected to be effective against it.
Any attempt to impose new restrictions is likely to meet with fierce resistance.
Tory Steve Baker, deputy chairman of the Covid Recovery Group of MPs, said: “Why on earth would we lock down when the vaccines continue to break the link between cases and hospitalisations and deaths?”
Greater Manchester Mayor Andy Burnham warned against attempts to impose local measures.
Mr Burnham, who battled the Government over Manchester’s restrictions last year, told the BBC’s Newscast: “We would be very concerned about the Government putting Blackburn, Bolton, anywhere to be honest, under local restrictions when the rest of the country is unlocking.”
PHE said cases of the variant and any clusters are being “rapidly investigated” by local PHE teams, councils and NHS Test and Trace to identify the contacts of those who test positive.
People are being encouraged to go for testing and to self-isolate if needed.
PHE said there were “many small dispersed clusters” in London and it was working with borough councils on a local approach, which had already been effective at driving down variants.
Dr Hopkins urged people to follow local public health advice and said: “Cases of this variant are rising in the community and we are continuously monitoring its spread and severity to ensure we take rapid public health action.”
PHE is asking the public to continue working from home and take up the offer of twice-weekly lateral flow tests.
Layla Moran MP, chairwoman of the All-Party Parliamentary Group on coronavirus, said: “The latest figures are deeply concerning and suggest the Government failed to act swiftly enough to prevent the Indian variant being imported into the UK.”
In other developments:
– Indoor pubs, restaurants and entertainment venues in Wales can reopen from Monday.
– Holidaymakers hoping to travel to Portugal on May 17 face uncertainty after the authorities in Lisbon extended the country’s “state of calamity” until the end of the month.
– Up to May 12 some 35,906,671 have received a first vaccine dose – a rise of 184,210 on the previous day – including some 18,890,969 who have received both doses, an increase of 452,437.
– A further 11 people had died within 28 days of testing positive for Covid-19 as of Thursday, bringing the UK total by that measure to 127,651.