The new online booking system for government-managed quarantine hotels appears to have suffered technical problems within hours of it going live.
Some users hoping to book their hotel quarantine stays from next week, as part of tougher border measures, have been met with a message that the new online portal was undergoing "maintenance" until 3pm on Thursday.
Problems have also been discovered with availability for the first two days of the new quarantine policy, which is due to come into force on Monday.
Sky News found that no hotels were immediately available at any of the eight sites for 15 and 16 February.
However, quarantine packages could be booked from 17 February.
The website's "maintenance" also appears to be preventing some people from booking the two extra COVID tests required of all arrivals to the UK from next week.
Under the new border measures being introduced, those arriving from all countries - not just those on the "red list" - will now be required to take a test on days two and eight after their arrival in the UK, as part of a 10-day quarantine period.
These will cost £210 per person in total.
Responding to the problems with the online portal, Labour's shadow home secretary Nick Thomas-Symonds posted on Twitter: "This is extremely worrying!
"Over a year into this pandemic and 50 days from the discovery of the South African strain, there are no excuses for yet more government incompetence in the introduction of hotel quarantine.
"Ministers must fix this - urgently."
A Department of Health and Social Care spokesperson said: "Rooms are available from Monday 15 February and travellers will be able to book through the site imminently.
"The website is undergoing maintenance to correct a minor technical issue."