Holidaymakers returning from “green” list destinations may instead have to pay for their pre-departure tests from May 17, when the ban on foreign travel is lifted.
The Government had proposed fast turnaround lateral flow tests would be made available free of charge to people travelling abroad to cut the hassle and expense of getting a pre-return test in a foreign country.
The free kits were due to be announced by Transport Secretary Grant Shapps on Friday when he unveiled the list of 12 safe “green” countries including Portugal, Israel, Gibraltar and Iceland.
But sources have told The Telegraph that the free kits may not now be allowed for use by May 17 because of the failure to reach “cross-Government agreement” on the scheme, amid concerns about validating the test results which are self-administered by travellers and their accuracy.
Instead, families will have to pay up to £20 for their pre-departure test on top of £60 for a second PCR test after their arrival back in the UK, a potential £320 bill for a family of four.
Government rules stipulate that travellers must present test results certified by their providers, who largely carry out the test themselves.
There is concern about how to validate the results of tests if they are self-administered by holidaymakers in their hotel rooms.
The test also currently has to meet a set Government standard of being sensitive enough to accurately identify more than 80 per cent of those with the disease and at least 97 per cent of those without it. This is why most of the pre-departure tests currently used are the more expensive PCR versions.
The average sensitivity of the lateral flow tests is 76.8 per cent, below the 80 per cent threshold, according to Public Health England and Oxford University research. The question of validation is thought to be the greater concern.
A source said: “It is more about the implementation than the science. How do you check the results? How do you validate them? Do people just turn up and show them?”
A couple returning from Mexico last week were refused boarding by BA after trying to present lateral flow test results.
A DfT spokesman said it was “working with the travel industry and private testing providers ahead of international travel reopening, to see how we can further reduce the cost of travel for the British public, while ensuring travel is as safe as possible."
A Department of Health spokesman said: "Testing remains an essential part of protecting public health.
“We are working with the travel industry and private testing providers to see how we can further reduce the cost of travel for the British public while ensuring travel is as safe as possible. This could include cheaper tests being used when holidaymakers return home, as well as whether the Government would be able to provide pre-departure tests."
Paul Charles, chief executive of travel consultancy The PC Agency, said: "Confidence to book future travel is based on the Government delivering the promises it has made and so it is crucial to urgently say whether the NHS lateral flow tests can be used for pre-departure testing.
"One of the ways to kickstart the recovery in the travel sector is to enable cheaper or free tests to be available."