Social measures will need to be in place for most of a year at least in order to control the spread of Covid-19, scientists advising the Government have agreed.

The Scientific Pandemic Influenza Group on Modelling agreed that, while the severity of measures could alternate during the period, "stricter" measures would need to be enforced for at least half of the year in order to keep cases at a level the NHS can cope with.

Strict measures could include school closures and social distancing for everyone, while less restrictive measures include isolating cases and households.

The Government published the papers today - a day after Prime Minister Boris Johnson said he expects the tide to be turned in the fight against Covid-19 within 12 weeks.

The report states: "It was agreed that the addition of both general social distancing and school closures to case isolation, household isolation and social distancing of vulnerable groups would be likely to control the epidemic when kept in place for a long period.

"It was agreed that a policy of alternating between periods of more and less strict social distancing measures could plausibly be effective at keeping the number of critical care cases within capacity.

"These would need to be in place for at least most of a year. Under such a policy, at least half of the year would be spent under the stricter social distancing measures."

The document says that the triggers for measures to be put in place or lifted could vary according to different regions.

There would be a two to three-week delay between measures being put into place and their impact being felt in intensive care units, it added.

On Thursday, the Prime Minister said the tide on Covid-19 could be turned in the next 12 weeks but added he could not promise that the UK would definitely be on a downward slope from the peak of the virus.

He said: "I cannot stand here and tell you that by the end of June we will be on the downward slope.

"It's possible but I simply can't say that for certain. Of course not, we don't know where we are, we don't know how long this thing will go on for but what I can say is that this is going to be finite, we will turn the tide and I can see how to do it within the next 12 weeks."

It comes as Chancellor Rishi Sunak plans to announce more emergency measures for workers.

He has been under pressure from Labour, unions and even senior Tory MPs to do more to help workers and the stalling economy weather the crisis.

He will reveal new measures on Friday at the daily Covid-19 press conference in Downing Street, where he is expected to be joined by Mr Johnson.