Lockdown measures to slow the spread of the coronavirus outbreak will be extended for at least three more weeks.

Wales’s First Minister Mark Drakeford announced the decision before Foreign Secretary Dominic Raab officially revealed the extension at the daily Downing Street briefing on Thursday.

Mr Raab, deputising for Prime Minister Boris Johnson as he recovers from the illness, said: “Any change to our social distancing measures now would risk a significant increase in the spread of the virus.”

He added relaxing rules could cause a “second peak” which would risk increasing deaths “substantially”.

Ministers agreed the need to prolong social distancing measures following meetings of the Cabinet and the Government’s emergency committee Cobra, amid signs the epidemic in the UK is beginning to peak.

The news came as the Department of Health said the Covid-19 death toll in hospitals in the UK had reached 13,729 as of 5pm on Wednesday, up 861 on the figure the day before.

Mr Raab said relaxing the lockdown would risk a significant increase in the spread of coronavirus.

Confirming an extension of the measures for at least three weeks, he said: “Earlier today I chaired meetings of the Cabinet and Cobra to consider the advice from Sage on the impact of the existing social distancing measures.

“There are indications that the measures we have put in place have been successful in slowing down the spread of this virus. But Sage also say that is a mixed and inconsistent picture and, in some settings, infections are still likely to be increasing.”

The rate of infection – the R0 value – was “almost certainly below one in the community”, meaning infected people were passing the disease on to fewer than one other person on average.

“But overall we still don’t have the infection rate down as far as we need to,” he told the daily Downing Street news conference.

Mr Raab, the acting prime minister in Boris Johnson’s absence, said there were still “issues with the virus spreading in some hospitals and in care homes”.

He added: “The very clear advice we received is that any change to our social distancing measures now would risk a significant increase in the spread of the virus.

“That would threaten a second peak of the virus and substantially increase the number of deaths.

“It would undo the progress we have made to date and as a result would require an even longer period of the more restrictive social distancing measures.”

The advice was that relaxing any of the measures would risk damage to public health and the economy, he said.

“Based on this advice, which we have very carefully considered, the Government has decided that the current measures must remain in place for at least the next three weeks.”