Francis Crick Institute the chief executive, Sir Paul Nurse, told the Covid-19 Inquiry it took three months for the DHSC to respond to a letter he sent along with research director, Sir Peter Ratcliffe, in April 2020.

The letter on 14 April expressed ‘great concern' about asymptomatic transmission of Covid between staff, commenting: ‘We therefore advise you to action an initiative that all NHS trusts and healthcare providers should be required to set up surveillance systems for the regular testing (both virological and serological) of all healthcare workers and patients with immediate effect.'

In its reply in July, the DHSC said: ‘Testing is a key part of the UK's response to Covid-19 and, following the publication of the Government's strategy, capacity has rapidly expanded.'

Testing was not offered to NHS staff unless they had symptoms, however, until November 2020.

Sir Paul said: The fact it was not put in place was a limitation on testing capacity, because I suspect they felt they couldn't do it, and rather than acknowledge that they couldn't do it, because that would have indicated a mistake in their overall strategy, they remained silent upon it.'

Hancock is due to appear at the inquiry next week.