The final stage of easing lockdown restrictions in England is to be delayed until 19 July.
It means most remaining curbs on social contact will continue beyond 21 June, when they had been due to be lifted.
The limit on wedding guest numbers will be removed but venues will still have to adhere to other rules.
Prime Minister Boris Johnson said there would be a review after two weeks and he was "confident" the delay would not need to be longer than four weeks.
However, he told a Downing Street press conference he could not rule out the possibility the date could be pushed back further.
Scientists advising the government had warned of a "significant resurgence" in people needing hospital treatment for Covid-19 if stage four of easing the lockdown went ahead on 21 June.
It comes amid rising cases, driven by the more transmissible Delta variant, which was first identified in India.
It means most remaining curbs on social contact will continue beyond 21 June, when they had been due to be lifted.
The limit on wedding guest numbers will be removed but venues will still have to adhere to other rules.
Prime Minister Boris Johnson said there would be a review after two weeks and he was "confident" the delay would not need to be longer than four weeks.
However, he told a Downing Street press conference he could not rule out the possibility the date could be pushed back further.
Scientists advising the government had warned of a "significant resurgence" in people needing hospital treatment for Covid-19 if stage four of easing the lockdown went ahead on 21 June.
It comes amid rising cases, driven by the more transmissible Delta variant, which was first identified in India.
