A scientist has quit the Government's pandemic advisory body amid a "concerning" coronavirus transmission rate in the UK.
Sir Jeremy Farrar left the Scientific Advisory Group for Emergencies (SAGE) at the end of October.
The British medical researcher, who works as director of the Wellcome Trust, was reportedly advocating for more mask wearing, ventilation and increased coronavirus testing this winter.
However, despite being urged to implement its Covid Plan B to curb the spread of the disease, the government has so far refused to do so.
In a statement to Sky News, Sir Jeremy said SAGE came under pressure during the pandemic and that the Covid-19 crisis is far from over.
He said: "The high levels of transmission seen in the UK remain concerning, but I stepped down as a participant of SAGE knowing ministers had been provided with most of the key science advice needed over the winter months.
"Throughout this crisis SAGE has provided vital evidence, and independent, expert, transparent advice to support the UK response, often under huge pressure."
After quitting SAGE, Sir Jeremy said his focus will now be to work at the Wellcome Trust - including research to support the end of the coronavirus pandemic.
Last year, Sir Jeremy said enough was known about coronavirus in January 2020 to act straight away, but the response was delayed.
The expert said that while information about the virus was "uncertain", action could have been taken.
Speaking at the Imperial College London's Abdul Latif Jameel Institute for Disease and Emergency Analytics's (J-IDEA) symposium on a post-Covid world in November last year, Sir Jeremy said: "The information you have early may be uncertain, but it's enough to act on.
"I would say that at the end of January we knew enough to have acted. And we waited. We waited out of uncertainty, we wanted to be more certain than we needed to be.
"But by the end of January, we knew that this was able to transmit asymptomatically, that it caused a nasty clinical syndrome and a significant number of people were dying, that healthcare workers were getting sick and distant family members were getting sick when people moved from Wuhan to Sichuan, that this was going out of China into other parts of south-east Asia, that we had no diagnostics, no treatment and no vaccines.
"To me, at the time - and this is not in retrospect - I think that was enough to have acted then in ways that we delayed."
He added that in a fast-moving epidemic, if officials delay by days, or by weeks, then they will end up playing catch-up.
Sir Jeremy explained: "I think the lesson for me is, cope with the uncertainty, go with the information you have whilst gathering new information, and don't get behind the curve."
It comes after chief medical officer Dr Tony Holohan said Covid-19 is "circulating widely" but "we have the tools to limit its spread".
He said: "We know that vaccination is very successful at preventing severe illness and hospitalisation, and I urge anyone who still needs to get their Covid vaccine to do so.
"We also know that, even when vaccinated, we still need to practice basic public health interventions - washing our hands, opening windows, wearing masks and, most importantly, staying home when we have symptoms.
"These simple measures are very successful at breaking the chains of transmission of this disease.
"As we practice all elements of the public health advice, we keep ourselves, and our communities, safe."
According to the latest government figures, 33,865 further Covid infections have been recorded in the past 24 hours.
A further 293 people have died within 28 days of testing positive for the virus.
