There are now almost 3,000 cases of the India variant of Covid-19 in the UK - a jump of 28% in just two days.
Health Secretary Matt Hancock revealed the figure in the House of Commons, confirming surge testing had been extended to Bedford, Burnley, Hounslow, Kirklees, Leicester and North Tyneside.
The number of cases now stands at 2,967. On Monday, the Health Secretary told MPs it stood at 2,323 - which had already doubled in less than a week.
Earlier, Downing Street said said that the latest data on coronavirus infections had not shown any "sharp increases or significant areas of concern".
Speaking at Prime Minister's Questions, Boris Johnson said that the latest data had given him "increasing confidence" the vaccines were working.

The Prime Minister's official spokesman said: "We have regular data that is published daily that tracks through right down to a very granular level on things like case rates.
"That is the information that the Prime Minister is seeing. Currently in that data we are not seeing any sharp increases or significant areas of concern."
He added: "Clearly it is important to stress that we want to give more time to get more data in so we can make decisions on our approach on the next step."