People across England have told BBC News they are struggling to access coronavirus tests.
Health Secretary Matt Hancock said last week that no-one should have to travel more than 75 miles for a test, after the BBC revealed some were being sent hundreds of miles away.
But dozens have now reported being unable to book a swab at all.
The Department for Health and Social Care (DHSC) said testing capacity was targeted at the hardest-hit areas.
A significant rise in demand for testing led the government to reduce the number of appointments available in areas of lower prevalence, to prioritise areas with outbreaks.
This in turn led to people applying for tests being directed to centres sometimes hundreds of miles away.
But last Thursday Mr Hancock pledged to put in "immediate" solutions to make sure people did not have to travel more than 75 miles, effective from last Friday.
Since then, postcodes entered into the government's booking system return a message suggesting there are no testing centres or home kits available - even if you are an essential worker with symptoms.
A DHSC spokesperson said: "We are seeing a significant demand for tests, but if you have symptoms we urge you to get tested.
"New booking slots and home testing kits are made available daily."
'Complete nightmare'
Melissa, a GP in the north-west of England, applied for a test for her seven-year-old son on Tuesday after he developed a new continuous cough and changes to his sense of taste.
After being offered a test in Sunderland, about 130 miles away, she applied via her local NHS's staff portal - designed to prioritise health staff.
But this system directed her first to Telford, almost 100 miles away, and then to London, a distance of more than 200 miles.
No home kits were available.
"It was a complete nightmare," she said. "I had to cancel face-to-face appointments with patients, including baby clinics."
She added that this had become a common theme in NHS Facebook groups of which she was a member.
"The whole system is going to fall over.
"It doesn't feel like the infrastructure is there to support NHS staff going into winter."
This sentiment was echoed by a psychiatrist in an area currently subject to government intervention because of its high rate of coronavirus.
She found that no tests were available after developing all of the textbook coronavirus symptoms, including a cough and a fever.
'Glitch in the system'
Frances, in Suffolk, tried to apply for a test when her daughter developed a high temperature. She didn't think it was coronavirus but "the rules are the rules".
She had understood that anyone with a temperature should apply for a test, and was not able to send either of her children to school until she did.
"Their teachers need to be kept safe, their classmates need to be kept safe, we need to do the right thing," she said.
Frances, like Melissa, was also not able to get a home kit, and when she tried to get an appointment at a drive-through centre was told no test sites were found.
"It almost looks like a glitch in the system," she said.
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There are some suggestions that the problems with accessing tests have happened since schools have returned.
Mr Hancock has claimed 25% of people applying for tests are not eligible because they don't have symptoms, although his department did not say where this figure came from.
Meanwhile, NHS 111 data published on 11 September reported a rise in calls relating to children with symptoms that would make them eligible for a coronavirus test.
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