Boris Johnson will hold a Downing Street press conference on Monday at 6pm, No.10 has confirmed.

The Prime Minister is expected to announce a delay in lockdown restriction in England which were originally planned for June 21.

Mr Johnson will be accompanied by England’s chief medical officer Professor Chris Whitty and the government’s chief scientific adviser Sir Patrick Vallance.

The Prime Minister is expected to announce that the road map easing earmarked for June 21 will be delayed for four weeks to July 19.

Rising case rates and hospital numbers are likely to have persuaded ministers of the merits of postponing the last stage of the road map out of lockdown.

The Delta variant of Covid-19, first identified in India, is now responsible for up to 96% of new cases – with a 60% increased risk of household transmission compared with the Alpha variant, which originated in Kent last year.

And while the vaccine rollout is estimated to have already averted more than 14,000 deaths in older people, just under half of all adults in England are not yet fully vaccinated.

The proportion of people testing positive for coronavirus in England has increased in recent weeks.

Around one in 560 people in private households in England had Covid-19 in the week to June 5 – up from one in 640 in the previous week, according to estimates published on Friday by the Office for National Statistics (ONS).

It is the highest level since the week to April 10.

The announcement means that limits on numbers for sports events, pubs and cinemas are likely to remain in place, nightclubs will stay closed and people will be encouraged to keep up social distancing and working from home.

It comes after scientists spent the weekend defending a delay, saying that the rapid spread of the Delta variant first identified in India risks a substantial third wave of infection.

Linda Bauld, professor of public health at the University of Edinburgh, said that any delay to the plan for easing was “proportionate” to prevent further lockdowns.

She told LBC: “We need to buy some more time to have more people receive a vaccine.

“We’ve just got about half of people with a second dose and we know that in the face of this Delta variant, that second dose is really important to provide the protection that is needed to avoid more people going into hospital.”

She added: “If we can provide more protection to the population through vaccines, then it means that we won’t have to take a step back again… So this is why an additional four weeks, which is what we expect will be announced, I think is proportionate.”

Meanwhile, Professor Anthony Harnden, deputy chairman of the Joint Committee on Vaccination and Immunisation (JCVI), told the Today programme that experts were “still very worried about the small numbers percentage wise, but probably large numbers of people that are still unvaccinated in the higher risk groups”.

He added that the JCVI was “looking carefully at what the Scottish Government has done” with regards to urging over-40s to have their second dose at eight weeks, adding that “it seems to be a sensible strategy, and we will advise the Government accordingly”.