Video report by ITV News Political Correspondent Paul Brand
The health secretary has said it could take "weeks" to resolve issues around coronavirus testing after he admitted there are "operational challenges" related to a surge in demand.
There have been widespread complaints that the UK's testing regime is inadequate, with some people being forced to drive for hours to get a test, and others having to wait days for appointments or returned results.
NHS Providers, the body representing hospital trusts in England, earlier issued a plea to the government for the testing regime to improve, saying staff are being kept out of work unnecessarily because test shortages.
In a scathing review of the government's testing regime, the body said it is "clear" there are "capacity problems".
In a statement it said: "NHS staff are having to self-isolate in the absence of a test for either them or their loved ones, taking valuable NHS staff away from the frontline where they are needed."
Health Secretary Matt Hancock, speaking in the Commons, said a new prioritisation list would be published, setting out who will be at the front of the queue for tests, but he admitted it could be "a matter of weeks" before the problems are resolved.
"We have seen a sharp rise in people coming forward for a test, including those who are not eligible," Mr Hancock said.
"Throughout this pandemic, we have prioritised testing according to need. Over the summer, when demand was low, we were able to meet all requirements for testing, whether priorities or not.
"But as demand has risen, so we are having to prioritise once again and I do not shirk from decisions about prioritisation. They are not always comfortable, but they are important."
Acute clinical care is the top priority, Mr Hancock added, with social care next on the list.
Meanwhile, one care home manager told ITV News about the problems they are facing with testing, including long waits for results, if they get them at all.
Those working in the care sector now get weekly tests but the delays in obtaining results complicates matters.
"Some tests don’t even come back," care home manager Debbie Adams told ITV News.
"I’ve had one member of staff where it hasn’t come back, twice we’ve done it and we’re about to do it again.
"It’s over five days until we get the test back."
According to Ms Adams, the testing system has got worse since it was put in place.
Other care homes have told ITV News it has take more than seven days to get results, meaning it is time for them to get another test by the time the last one is completed.
Meanwhile, shadow health secretary Jonathan Ashworth accused Mr Hancock of "losing control of this virus".
NHS Providers chief executive Chris Hopson said there was a lack of detailed operational information on the shortages, such as how long they will last, which means hospitals are having to work "in the dark".
“It’s clear that there are current capacity problems with the testing regime," he said, adding how trust leaders across the country had "all raised concerns" about the "lack of testing" leading to "greater levels of staff absence".
“It’s not just access for tests for staff members themselves, it’s also access for their family members as NHS workers have to self-isolate if their family members are unable to confirm if they have Covid-19 or not.
“The problem is that NHS trusts are working in the dark – they don’t know why these shortages are occurring, how long they are likely to last, how geographically widespread they are likely to be and what priority will be given to healthcare workers and their families in accessing scarce tests."
He said bosses need to this information so they can "plan accordingly", for example by establishing their own testing facilities.
Meanwhile Labour has called on the Government to set out a “clear winter plan” to protect care homes amid signs they are experiencing a new rise in Covid-19 cases.
Home Secretary Priti Patel defended the testing regime, saying the government has "always prioritised people on the front line and in the NHS".
She insisted the "priority has been constantly to bolster and increase testing capacity in the areas where they need it most".
But she admitted "much more work" needs to be undertaken with Public Health England and public health bodies in those particular local areas.
Leader of the House of Commons Jacob Rees Mogg, on his way out of a Cabinet meeting, claimed testing is "actually a government success".
"I think it's going as well as can possibly be expected, considering the demand."
NHS Providers say the capacity issues are causing a huge ripple effect throughout the health service, with a lack of tests not only forcing staff out of work, but also keeping patients away from treatment.
“We’re aware of a small number of examples of patients being unable to get such tests, which cuts across trusts’ ability to restore services in the way they have been asked to do,” Mr Hopson said.
“We are concerned, for example, that patients waiting for hospital treatment can no longer highlight this fact when applying online to access a test.
“We need to prioritise tests for healthcare workers and their families and patients coming in for treatment, many of whom have already waited longer than normal.
“Our recent survey showed how concerned trust leaders were about the impact of inadequate testing on their ability to restore services and it’s disappointing that no detailed information on the current problems has been shared.”
NHS Providers has urged the Government to be more “honest” over problems with coronavirus testing as a senior doctor said a “fit for purpose” system is needed now.
Mr Hopson accused the government of being more concerned about dealing with the political implications of operational problems, rather than fixing them.
"The government response has often been to rely on a random, impressive sounding, overall statistic - the number of tests performed or PPE items delivered - or to set out a bold future ambition - a world class test and trace service by June, or a moonshot testing regime at some point next year."
He said trust leaders are "frustrated" that throughout the pandemic "the government has always seemed more concerned with managing the political implications of operational problems rather than being open and honest about them".
Those approaches “ignore the operational problem at hand”, he said.
He cited shortages of PPE and testing reagents earlier in the crisis as being "good examples" of government failings.
Health Secretary Matt Hancock admitted last week that there had been “challenges in access to tests” but insisted that “the vast majority of people get their tests rapidly and close to home”.
Residents in Bolton, where the infection rate is the highest in England, have complained of long delays in trying to book a test and in some cases being offered appointments in other areas of the UK.
Council chiefs have urged the Government to treat “major flaws” with the online booking system for tests as “a matter of the utmost priority”.
Council leaders in Sefton, Merseyside, and Bury, Greater Manchester, urged people to only apply for a test if they had symptoms or had been asked to do so, amid reports of a rise in requests from those without symptoms.
An NHS spokeswoman said hospital labs have been asked to “further expand their successful, fast-turnaround and highly accurate testing capacity” to support the test and trace programme.
The World Health Organisation’s director-general Tedros Adhanom Ghebreyesus said on Monday that testing was one of the “public health basics” countries need to do well to be able to “reopen their societies, economies and borders safely”.