The Prime Minister warned that the Indian coronavirus variant could “pose a serious disruption” to plans to ease restrictions and “could make it more difficult” to end them as hoped in June.

The Prime Minister told the Downing Street press conference: “I do not believe that we need, on the present evidence, to delay our road map and we will proceed with our plan to move to step three in England from Monday.

“But I have to level with you that this new variant could pose a serious disruption to our progress and could make it more difficult to move to step four in June.”

The message came as Boris Johnson led a Downing Street press conference alongside England's chief medical officer professor Chris Whitty.

Boris Johnson said that if the Indian variant proves to be “significantly more transmissible” than other strains “we’re likely to face some hard choices”.

The Prime Minister told the Downing Street press conference: “I’m told that if it is only marginally more transmissible, we can continue more or less as planned but if the variant is significantly more transmissible we’re likely to face some hard choices.”

But he said there is “no evidence to suggest that our vaccines will be less effective in protecting people against severe illness and hospitalisation”.

Second doses of coronavirus vaccines will be accelerated for the over-50s and the clinically vulnerable across the country to be given eight weeks after the first dose amid a rise in cases of the Indian variant.

While Covid-19 cases in most areas of the UK are at their lowest levels since August last year, there are concerns the Indian variant could see cases jump back up.

At present, there is no evidence the B16172 variant is resistant to current vaccines.

Health Secretary Matt Hancock has previously said the situation was being monitored carefully and the Government “will not hesitate to take further action if necessary”.