The easing of lockdown restrictions in Britain has been described as "very dangerous" by a top government adviser, with thousands still flouting official advice.

The coronavirus restrictions ease again on Monday - allowing people to meet in groups of up to six as long as they practise social distancing guidelines.

Professor Jonathan Van-Tam, the deputy chief medical officer, called for people to obey the new rules and expressed fears of a second wave if they were ignored.

He told the daily Downing Street press conference on Saturday that the Government and the public had a "dual responsibility" to prevent a second wave of the virus.

He added: "I believe this is also a very dangerous moment. We have to get this right."

It comes after thousands of people flouted the rules on Saturday and were spotted gathering in large groups at beaches, parks and beautyspots, with many pictured boozing in the sun.

Packed crowds were spotted at Durdle Door in Dorset, with sunbathers herded together so helicopters could land after four people were seriously injured cliff-jumping.

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A family wearing protective visors enjoy the sunshine at Ruislip Lido in west London

Prof Van-Tam said scientific opinions "always vary to some extent", and told the press conference that the lockdown easing must go "painstakingly" slowly.

He added: "This is a dual responsibility here of Government to go slowly and carefully and to take the advice from the scientists.

"Of the scientists, to watch this whole thing very closely over the next few weeks. And, of the public in general to actually follow the guidance.

"Don't tear the pants out of it, and don't go further than the guidance actually says."

Declaring that "football is coming back", Mr Dowden said: "Football, tennis, horseracing, Formula 1, cricket, golf, rugby, snooker and others are all set to return to our screens shortly.

"I'm glad to confirm today that a third of matches to finish the season will now be free to view including the Liverpool v Everton derby and live Premier League football will be on the BBC for the first time in its history."

Thousands of people have been enjoying the warm weather this weekend

Asked for his response to experts who have expressed concern the lockdown is being eased too quickly in England, Mr Dowden said it must be remembered there are more than 50 scientists in the Scientific Advisory Group for Emergencies (Sage), "all of whom will have their different perspectives".

He told the daily briefing that scientists are "absolutely right to urge caution".

But Professor Robert West, a participant in the Scientific Pandemic Influenza Group on Behaviours (SPI-B) which advises Sage, emphasised on Saturday that some 8,000 infections and 400 deaths a day are still occurring.

The Observer reported that a letter sent by 26 senior UK academics and health administrators to Downing Street complained about the impact of the Dominic Cummings controversy.

The group also warned about a failure to enact an effective test, trace and isolate system to pinpoint and then quarantine newly infected people.

As a result, they are now "very concerned for the safety and wellbeing of the general public" as the lockdown measures are relaxed, the newspaper reported.

People crowd Durdle Door beach, near Lulworth in Dorset, before the incident

The easing of England's lockdown will also signal the reopening of schools to allow more students to return, while outdoor retailers and car showrooms are also able to reopen.

Asked if he agrees it is too soon to ease more of the lockdown, Prof Horby told BBC Radio 4's Today programme: "Actually, I do. We have still got 8,000 cases a day."

He added that although measures taken so far "have been very successful in... decreasing the numbers", it is vital "we don't lose control again".

He said one of the key issues is the NHS Test and Trace system, which has been rolled out across England with the help of 25,000 contact tracers.

But the programme will not be operational at a local level until the end of next month, while an accompanying app is delayed by several weeks.

Prof Horby added: "We are entering a period where there is a risk of increasing transmission, but we don't yet have that safety net fully in place."

In Scotland, people can now meet others from one other household at a time as long as it is outdoors, but social distancing should continue and groups must be a maximum of eight people.

People in Wales will be allowed to meet up with others outdoors from Monday.

In Northern Ireland, more retailers can open and small outdoor weddings will receive the go-ahead from June 8 if the coronavirus infection rate remains under control.