Pressure is growing on the government to do more to tackle Covid test shortages, with calls for NHS staff to be prioritised amid surging numbers of patients in hospital with the virus.
On Thursday the number of patients in hospital with coronavirus in England climbed to its highest level since February.
Ministers have been told health workers should come first when trying to access lateral flow tests (online and in pharmacies) amid concerns over staff shortages linked to Covid-19.
The British Medical Association (BMA) has urged the government to "do everything possible to ensure that enough tests are available for key workers as a priority," pointing to 18,000 staff absences across acute hospital trusts in England.
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Concerns persist over difficulty accessing Covid tests across the country.
The public has faced issues ordering online tests in recent days, while pharmacies have also complained about patchy supplies of lateral flow kits.
Much of the UK was hit by intermittent availability of slots at PCR test centres on Thursday and the option to order them online.
In a letter to MPs, Health Secretary Sajid Javid said the supply of lateral flow tests was being tripled in January and February from a pre-Omicron plan of 100 million to 300 million per month.
However, he said ministers expect a need to "constrain" the system at certain points over the next two weeks.
The BMA warned it expected higher numbers of staff absence when the most recent data is published later this week.
Dr Chaand Nagpaul, BMA chair of council, said: "The government has pledged that eight million lateral flow kits will be sent to pharmacies before New Year’s Eve.
"That’s a step in the right direction but there is no assurance that key workers will be offered them first.
"The BMA is urging the government to do everything possible to ensure that enough tests are available for key workers as a priority."
The Royal College of Nursing (RCN) echoed the call for health workers to come first when trying to access the rapid coronavirus tests.
NHS workers have shared their experiences of difficulties getting hold of tests.
Dr Azeem Majeed, head of primary care and public health at Imperial College London, told Times Radio: "I struggled to get a test recently. I am required to test twice a week as an NHS worker but when I log on to the online site, there’s often none in stock.
"It’s not just NHS staff but other key workers too, such as social care workers, police, fire service and so on, who need these tests as well so it is worrying that they’re in such short supply at the moment."
Dr Majeed called for workers in "key groups" to be prioritised "to ensure our NHS can function, our schools can function, that our society can function well."
Shadow health secretary Wes Streeting also called for NHS workers to be put "at the front of the queue" for tests.
On Thursday, the Welsh Government announced it would loan England four million lateral flow tests, bringing the total the country has given England to 10 million.
First Minister Mark Drakeford said: "Wales has a significant stock of lateral flow tests, sufficient to meet our needs over the weeks ahead."