A UK Government health chief has been panned by scientists after claiming no-one could have predicted Covid-19 would mutate.

Baroness Dido Harding also warned that around 20,000 people a day contacted by England’s Test and Trace system are not fully complying with instructions to self-isolate.

The comments came as she appeared in front of MPs on the House of Commons Science and Technology Committee.

The Tory peer, who heads the National Institute for Health Protection after being promoted from her former role running England’s test and trace system, warned that the so-called Kent variant has now become "endemic" and accounts for more than 70% of cases in England.

She added: "Between our business plan being published and us going into the lockdown we're in now, we've seen the virus mutate, we've seen the new variant emerge – which is something that none of us were able to predict."

That assertion was rubbished by Linda Bauld, professor of public health at the University of Edinburgh.

The National: Professor Linda Bauld

She told The National: "Coronaviruses such as SARS-Cov-2 do change more slowly than most other RNA viruses, but the research community have been documenting changes since the original genetic code was released from China.

“So it’s not the case that mutations were unexpected. We couldn’t predict exactly which variants would emerge but certainly ones that were more transmissible or even one that could result in more severe illness should have been factored into any future planning."

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Several leading scientists concurred with that assessment and countered Dido’s claim on social media.

Clare Wenham, assistant professor in global health policy at the London School of Economics, commented: “No-one [predicted the variants], except all the scientists.”

Dr Xand van Tulleken added: “It is a rule of biology – like gravity in physics – that viruses mutate. Literally anyone w A-Level biology could have answered the ‘will it mutate?’ question correctly.”

Harding was also asked to address concerns about the number of people who are self-isolating under the test and trace system she set up.

The baroness faced further questions about cronyism, but denied there were "conflicts of interest" with anyone awarded a contract with NHS Test and Trace.

Harding said that research has shown that between 20% and 40% of people contacted by the programme are not fully self-isolating after being instructed to do so.

Based on the rates of people contacted on a daily basis, an optimistic estimate suggests that 20,000 are not fully following self-isolation instructions, MPs heard.

Harding said there could be multiple reasons behind people ignoring the rules, including confusion over the rules, a lack of funds and mental health impacts.

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Taking last week's total number of cases and contacts, around 700,000 – which equated to 100,000 a day – she concluded that 20,000 a day are not isolating.

Responding to questions from former health secretary Jeremy Hunt, she said: "Could I add a slight complexity to your calculation which actually might well make your number go up a bit, which is that's the proportion that we know about."

Harding said her biggest concern is the people who feel ill but do not come forward for testing.

Hunt commented: "Thousands of people a day is enough to restart the pandemic."

Harding also revealed there were 2500 consultants working on the project employed in roles surrounding "technical operational process and system design".

They are paid an average of £1100 a day, MPs heard. It is hoped that many of these roles will be transferred to civil service roles, Harding said.