Matt Hancock has said a new, faster-spreading variant of Covid-19 might be behind the recent surge in cases in London.

Speaking at a press conference on December 14, the health secretary said a new variant of the virus has been identified.

He said this may explain the fast rise in cases in the south of England as he announced that London, along with south and west Essex and the south of Hertfordshire, will be going into Tier 3 as of midnight on Tuesday night.

"We have identified a new variant of coronavirus, which may be associated with the fastest spread in the south-east of England.

"Initial analysis suggests that this variant is growing faster than the existing variants.

"We’ve currently identified over 1,000 cases with this variant, predominantly in the south of England, although cases have been identified in nearly 60 different local authority areas, and numbers are increasing rapidly."

The WHO has been notified, but Mr Hancock added there is nothing to suggest this will cause a more serious illness, and nothing to suggest it won’t respond to treatment.

In his speech, he pointed out the very large exponential growth in the virus in these areas, as well as Kent.

"We do not know the extent to which this is because of the new variant," says Hancock - but he says we have to take “swift action”.

The virus isn't just spreading in younger people, but in all age groups including the over 60s, he says.

"We must act now to shift the curve because... there is not a moment to spare," he says, adding that ministers are acting ahead of the formal review date on Wednesday.

Shadow health secretary Jonathan Ashworth says given the data no one can be surprised that new areas are moving into tier 3.

He notes that the government was warned that tier 2 "wouldn't be enough to contain the spread".

"We are heading into Christmas with diminishing headroom," he says.

Ashworth argues that the response "could have been strong if contact tracing had been better" and urges the government to put public health teams in charge of contact tracing, rather than the company Serco.