Boris Johnson's government has become embroiled in a political row after it emerged the British Prime Minister's chief adviser attended meetings of the main scientific group advising ministers on the coronavirus pandemic.

Downing Street was forced to deny that Dominic Cummings and another adviser, Ben Warner, were members of the politically independent Scientific Advisory Group for Emergencies (SAGE).

However, following reports in The Guardian newspaper, the government admitted that Mr Cummings had sat in on group meetings, prompting the opposition Labour Party to ask for "answers" over his exact role.

The medical director of NHS England has declined to comment on whether or not Mr Cummings made contributions to a meeting of scientists advising the Government on the coronavirus outbreak.

Professor Stephen Powis was asked whether or not Mr Cummings made a contribution. He replied: "It's the scientists that make the scientific contributions and the scientists and experts in that group, that are absolutely involved in generating the advice."

The row emerged as the Britain's general Covid-19 approach came under increasing scrutiny, as the official death toll approached 20,000 in one of the countries worst hit by the pandemic.

NHS England medical director Prof Stephen Powis speaking today at a media briefing

In a statement, a Number 10 spokesman said: "It is not true that Mr Cummings or Dr Warner are 'on' or members of SAGE.

"Mr Cummings and Dr Warner have attended some SAGE meetings and listen to some meetings now they are all virtual. 

"They do this in order to understand better the scientific debates concerning this emergency and also to understand better the limits of how science and data can help government decisions."

Latest coronavirus stories

The statement added that it was "factually wrong and damaging to sensible public debate" to suggest the committee's advice was affected by the government.

Until now, membership of the committee, which is a key body in shaping the UK's response to the pandemic, has not been made public.

Labour's health spokesman, John Ashworth, told BBC radio today that his "concern" was "that political advisers have influenced the debate".

"The way to clear this up is for all the minutes to be published; we've called on the government to do this," he said.

The UK government has come under increasing pressure on a number of fronts in recent weeks, including criticism over shortages in personal protective equipment and a lack of widespread testing, particularly of frontline health and social care workers.

Questions have also been asked why it was slow in enforcing a nationwide lockdown to enforce social distancing measures.

Police asking sunbathers to move on in sunny London Fields park today

There are also growing demands for a government exit strategy from the current lockdown, first imposed on 23 March, extended on 16 April and due for review on 7 May, as concerns grow over the huge impact the crisis is having on the economy.

Meanwhile, a new website offering testing for up to 10 million key workers and their families has been overwhelmed.

And this morning, health officials announced that as many as 5,000 severely ill coronavirus patients could be treated with plasma from people who have recovered from the illness as part of a new approach.