Video report by ITV News Political Correspondent Daniel Hewitt
The government has closed applications for essential workers to have coronavirus tests - just hours after first opening - due to "significant" demand.
As well as stopping bookings for drive-through centres, the 5,000 home testing kits which were available to order ran out within two minutes of applications opening.
A Downing Street spokesman added the Government hoped to have 18,000 daily home testing kits available for key workers by the “end of next week”.
Applications will reopen on Saturday when the government says there will be more tests available to book.
The government said there is capacity for 15,000 drive-thru tests per day, all of which have now been used.
The Department of Health (DoH) has said it is working to "rapidly increase availability".
The government has said it wants to be carrying out 100,000 tests each day by the end of April.
Earlier on Friday, applications had closed and then reopened due to what a spokesperson described as "enormous" demand.
Mr Shapps dismissed suggestions that the website allowing critical workers to book tests had crashed.
He said: “There were reports that the website had crashed, which it hadn’t, it was simply that the slots for today were taken up."
"We’ve seen in the last few days this difference between the capacity available, I think the last figure I saw was 51,000, and the number of tests done, 28,000 yesterday."
He added: "I can tell you 16,000 of those were booked during the first period of that being online and the site has actually been brought back up around now for more people to go and book sites, it will then close off again, more tests will become available tomorrow and so on."
The demand for tests follows Health Secretary Matt Hancock's announcement that people whose work is critical to the Covid-19 response and those they live with, will be able to register for a test if they have symptoms.
It means NHS and social care staff, police officers, teachers, social workers, undertakers, journalists and those who work in supermarkets and food production are among those now eligible.
Mr Hancock set out his plans for “easier, faster and simpler” testing so that more people can access a Covid-19 test to tell them whether they have the virus.
He said people can register for a test at www.gov.uk/coronavirus.
When the website is up and running, after registering, people will receive a text or email with an appointment at a drive-through centre or can request a home test kit, although the latter are in limited supply.
A help desk has been established to aid the process, while mobile units run by the Army are travelling around the country to where they are needed, such as care homes.
Asked whether the Government was confident people would be able to test themselves accurately with a kit sent to their homes, the spokesman added: “There are videos available to show people how to do this and people will be given clear instructions.
“We would hope they would be able to do this, yes.”
Number 10 confirmed the Government is trusting that those applying for testing are key workers, with no eligibility checks in place for online bookings.
The official spokesman said: “As with many other aspects of the coronavirus response, we would expect the public to respond in good faith.
“That is what they have done with other aspects of the scheme, I think we’d expect it to be the same here.”
Test results from the drive-through sites will be sent out by text within 48 hours, and within 72 hours of collection of the home delivery tests.