Government advisers have voiced concerns the easing of lockdown measures from Monday will come too soon and could cause a spike in the spread of coronavirus.

Scientists Sir Jeremy Farrar and Professor John Edmunds, both members of the Scientific Advisory Group for Emergencies (Sage) - which advises the Government on the Covid-19 - said ministers were taking risks by following their current plans.

They expressed concern at allowing the gradual reopening of shops and schools and larger gatherings to meet in private while the number of new cases each day remains "relatively high".

Sir Jeremy also said the newly-introduced NHS test-and-trace system needed to be "fully working" before measures were eased.

Meanwhile, a tranche of papers released by Sage revealed advice given to the Government in April said it was "likely" the R-value - the average number of people that will contract coronavirus from an infected person - would go above one should non-essential shops be reopened.

The comments come as Britain is set for a weekend of high temperatures and police have urged the public to follow current safeguards about social contact ahead of the lessening of restrictions, which will allow up to six people to meet outside if social distancing is observed.

In a Twitter post, Sir Jeremy said: "Covid-19 spreading too fast to lift lockdown in England. Agree with John & clear science advice.

"TTI (test, trace and isolate) has to be in place, fully working, capable dealing any surge immediately, locally responsive, rapid results & infection rates have to be lower. And trusted."

A document on a Sage meeting from April 13, released on Friday, showed the Scientific Pandemic Influenza Group on Modelling (SPI-M) that advises the Government warned against reopening shops and leisure facilities.

The document said: "There is limited evidence on the effect of closing of non-essential retail, libraries, bars, restaurants, etc, but it is likely that R would return to above 1 and a subsequent exponential growth in cases."

Downing Street warned the public that meet-ups remain prohibited until after the weekend.

The Lake District National Park Authority has urged people to "show care and consideration for everyone who lives and works" in the area, while Dorset Police has told people to "go home or elsewhere" if an area looks too busy.

Wiltshire Police Chief Constable Kier Pritchard said: "I know we are going into another weekend where the weather looks fantastic and beautiful, and that will bring many temptations for us to go outside and perhaps meet with friends and loved ones that we haven't seen for some time, and perhaps gather in large groups, but, quite simply the rules and regulations will not allow that this weekend."

Elsewhere, Chancellor Rishi Sunak said self-employed workers will be eligible for a second and final coronavirus grant and confirmed employers must start paying towards the wages of furloughed staff from August.

Mr Sunak said the schemes had been a "lifeline" for millions of people and businesses, but that as the country comes through the "other side" of the Covid-19 crisis, it was time to adjust them to "ensure those who are able to work can do so".

He has extended the self-employment income support scheme - which has so far seen 2.3 million claims worth £6.8 billion - enabling freelancers to access grants of up to £6,570 from August. Individuals could claim up to £7,500 under the first grant, which launched earlier this month.

Shadow chancellor Anneliese Dodds welcomed the extension, but said it was "concerning that there is no commitment within these plans for support to only be scaled back in step with the removal of lockdown".

Elsewhere:

- A National Association of Head Teachers poll found nine out of 10 headteachers will open their schools from Monday, according to The Times, although three in four will not follow government guidance on how many pupils to bring back

- Border Force and police officials fear plans to quarantine travellers entering the UK for 14 days are "unenforceable", reports the Daily Mail, and the Prime Minister could "water down" the scheme or cancel it completely

- The total number of UK deaths involving Covid-19 has now passed 48,000

- Scientists advising the Government suggested only around half of people with coronavirus symptoms self-isolate for a week, raising concerns over the ability to prevent future outbreaks

- Nearly 17,000 fines for alleged breaches of coronavirus lockdown rules have been issued by police in England and Wales, according to figures from the National Police Chiefs' Council

Meanwhile former prime minister Theresa May says Dominic Cummings did not "follow the spirit" of the lockdown guidance.

In a letter to her constituents in Maidenhead, Berkshire, Mrs May said said she can "well understand the anger" of people who had obeyed the guidance while the PM's aide drove from London to a family farm in Durham.

She added: "In these circumstances I do not feel that Mr Cummings followed the spirit of the guidance.

"I can well understand the anger of those who have been abiding by the spirit of the guidance given by the Government and expect others to do so."

But Mrs May added she was concerned that the focus on Mr Cummings was "detracting from the most important task" of dealing with coronavirus.