People wanting to check whether or not they are infected with coronavirus have again been left frustrated after more problems getting hold of tests.

Government websites reported that rapid lateral flow tests were “not available right now”, the third day of problems, as demand surged.

People trying to book walk-in PCR tests also encountered problems, being told they were “not available right now”.

Elsewhere, the vaccine booster rollout was again met with reports of queues at medical centres, and on the Government’s website.

UK Health Security Agency sources said on Tuesday that “exceptionally high demand” for the in-person PCR tests had created pressure on the system and led to temporarily reduced availability in some areas.

Difficulty getting access to tests is particularly significant, with new rules now in place requiring proof of double-vaccination, or a recent negative test, to enter certain venues such as nightclubs and large sporting events.

It comes as Dr Jenny Harries, chief executive of the UK Health Security Agency, told MPs that the Omicron coronavirus variant was “probably the most significant threat we’ve had since the start of the pandemic”.

Those testing positive for coronavirus from now will likely be in isolation until at least Christmas Day.

The Government website states those testing positive will need to self-isolate from the day symptoms started and the next 10 full days.

People may need to self-isolate for longer if they get symptoms while self-isolating or if the symptoms do not go away.