The Government is facing calls for greater transparency over the scientific advice given to ministers on the coronavirus outbreak.

Downing Street angrily dismissed claims the advice could be politicised following the disclosure Boris Johnson’s top aide Dominic Cummings had been attending meetings of a key scientific group.

Opposition parties, however, said political advisers had no business attending the Scientific Advisory Group for Emergencies (Sage) and called for its deliberations to be opened to wider scrutiny.

The row came as the coronavirus lockdown was entering its fifth weekend with fears that the expected warm weather for much of the country may see people ignoring social distancing rules.

More than 19,000 people have now died in hospital after testing positive for coronavirus in the UK, with many more deaths expected in care homes.

Meanwhile, it emerged that talks have been taking place between ministers and the Premier League on re-starting the football season once the Government decides the conditions for easing the lockdown have been met.

The controversy over Sage – which will advise ministers on the lifting of the restrictions – came after The Guardian reported that Mr Cummings and Ben Warner, a data scientist who worked with him on the Vote Leave campaign in the Brexit referendum, had been present at Sage meetings.

Downing Street denied they were members of the group and said they were simply seeking to better understand the science involved and how it could inform government decision-making.

“Sage provides independent scientific advice to the government. Political advisers have no role in this,” a No 10 spokesman said.

“The scientists on Sage are among the most eminent in their fields. It is factually wrong and damaging to sensible public debate to imply their advice is affected by government advisers listening to discussions.

“Public confidence in the media has collapsed during this emergency partly because of ludicrous stories such as this.”

However, shadow health secretary Jonathan Ashworth said the disclosure raised “significant questions” about the credibility of Government decision-making.

“Dominic Cummings has no place on the Government’s scientific advisory group on the coronavirus,” he said.

“He is a political adviser, not a medical or scientific expert. If the public are to have confidence in the Sage, the Government must make clear Dominic Cummings can no longer participate or attend.

“We also need full transparency on who is attending meeting of Sage what is being discussed.”

Meanwhile, it has emerged that Culture Secretary Oliver Dowden has been in talks with the governing bodies of a number of major sports, with football expected to be the first to get the green light to resume matches behind closed door.

It is understood that detailed discussions have been taking place with medical officials from Public Health England on the criteria that would have to be met for games to go ahead.

A Government spokesman said: “Ministers continue to work with sports governing bodies on how live sporting events can resume in the future.

“This can only happen once we have passed the five tests for easing social distancing measures.”

In other developments, the NHS is to launch a new campaign urging people to seek urgent care if they suffer a medical emergency after visits to A&E dropped by almost 50%.

Health officials are worried many people are not seeking treatment because they fear contracting Covid-19 in hospital, jeopardising their survival and potentially becoming collateral damage to the virus.

The Government has also given the go-ahead for a clinical trial to establish if plasma from the blood of recovered coronavirus patients could help treat others fighting the illness.

The treatment would involve the “convalescent plasma”, donated from the blood of people who have recovered from the virus, being transfused to patients who are struggling to produce their own antibodies against the illness.

Convalescent plasma was used as a treatment during the Sars outbreak.

Thousands of people are also expected to try to book a coronavirus test on the Government’s new website again on Saturday, after tests ran out soon after it went live on Friday.

Some 46,000 people tried to book a test, with more than 10 million key workers and their households now eligible for one as the Government races to hit its 100,000-a-day testing target by next Thursday.

Under the expansion, NHS and social care staff, police officers, teachers, social workers, undertakers, journalists and those who work in supermarkets and food production are among those now eligible.

But within two minutes of the website going live at 6am on Friday, all 5,000 tests for people to do at home had been booked, while more than 15,000 appointments for tests at drive-through centres were also taken quickly.

The Department of Health said a total of 19,506 patients had died in hospital after testing positive for coronavirus in the UK as of 5pm on Thursday, up by 768 from 18,738 the day before.