Boris Johnson has announced that all travel corridors to the UK will be closed from Monday in an effort to halt the spread of “as yet unidentified new strains” of coronavirus.

Britain’s prime minister made the announcement on Friday amid a mixed picture in the UK’s efforts to tackle Covid-19. The latest figures stated another 55,761 positive tests for the disease — continuing the falling trend over the past seven days — but 1,280 further deaths were recorded.

Mr Johnson said these “additional steps” on restricting travel were necessary to tackle any new strains. Individuals travelling to the UK will need proof of a negative test taken 72 hours prior to departure and will be required to fill out a passenger locator form.Passengers will also be expected to self-isolate for a 10-day period after landing, with “substantial fines” for those who fail to adhere to the rules. The measures will be in place for at least a month.

Mr Johnson said: “It is vital to take these extra measures now when day by day, hour by hour, we are making such strides in protecting the population.”

On Thursday, the UK banned most people arriving from South America and Portugal under tough measures to try to control the spread of a strain of coronavirus first identified in Brazil.

The government announced that more than 3.2m people had been vaccinated, including almost 45 per cent of the over-80s and around 40 per cent of older residents in care homes.

But Chris Whitty, England’s chief medical officer, warned that deaths would continue to rise for some days and would not drop until the vaccine had been delivered to a greater proportion of the population.

“The number of people entering into hospital is still rising in most parts of the country and the number of people in hospital is still rising in most parts or all parts of the country,” he said.

Patrick Vallance, England’s chief scientific adviser, said the nationwide lockdown was key to reducing infections and it was too soon to consider relaxing any restrictions. “Take the lid off now and it is going to boil over for sure,” he said.

Despite the adverse impact to the travel industry of ending travel corridors, businesses accepted the move as necessary to thwart the spread of the disease.

Airlines UK, an industry association representing airlines, said “travel corridors were a lifeline for the industry last summer and the government was right to bring them in when it did”.

“But things change and there’s no doubting this is a serious health emergency and ministers need to act to keep borders safe and the public protected.”

Abta, the trade body for the travel industry, called on the government to provide further support for the travel sector. “The government needs to address this as a matter of urgency, not only for the jobs and businesses at risk in the sector, but in recognition of the important role the travel industry will play in the UK’s economic recovery and achieving their vision of a global Britain,” it said.

The CBI business lobby group said the closure of the corridors meant “close co-ordination with business and further measures to rebuild demand will be essential for re-energising the aviation sector”.

“While done with the best of intentions this will undoubtedly come as a further blow to [the] aviation industry, which has already suffered significantly during the crisis, highlighting the need for targeted fiscal support,” it said.

Labour leader Keir Starmer said the move to close travel corridors was the “right step” but questioned the timing. He said the public would be thinking: “Why on earth didn’t this happen before?”