A public health expert has warned that lateral flow tests 'expire very quickly' and encouraged the government to update its guidance.
They also said the infectiousness of the Omicron variant should push people to wait to use lateral flow tests until just before meeting up with others.
Irene Petersen, a professor of epidemiology at University College London, said official advice should be updated as those infected with Omicron "may switch from being non-infectious to infectious within hours".
Current guidance from the government recommends taking a test "if you will be in a high-risk situation that day". READ MORE: The Omicron symptom that only occurs while you are sleeping However, Prof Petersen told The Sunday Telegraph: "That’s not good