The apparent infectiousness of the Omicron variant should push people to wait to use lateral flow tests until just before meeting up with others, a public health expert has warned.

       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”.

       Government guidance currently recommends taking a test “if you will be in a high-risk situation that day”.

       Prof Petersen told The Sunday Telegraph: “That’s not good enough. We’re seeing so many examples now where people have taken a test a day before and then when they take one the day after they are positive.

       (PA Graphics)

       (PA Graphics)

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       “Omicron is very, very fast, so the test result expires very quickly. It is hours that we are talking about now.”

       The latest figures from the UK Health Security Agency showed there had been 10,059 additional confirmed cases of the Omicron variant of Covid-19 reported across the UK, bringing the total confirmed cases of the variant across the four nations to 24,968.

       The variant’s rapid spread means tougher restrictions could soon be introduced after experts warned there are likely already hundreds of thousands of new infections every day.

       Stricter measures could be imposed after Boxing Day, according to a report in The Sun newspaper, which said the contingency plan had not yet been presented to ministers.