The prime minister is continuing to study data on cases, hospitalisations, deaths and vaccinations ahead of a Monday press conference at which he will set out the plan for England’s road map out of lockdown.
Downing Street has insisted no decisions have been taken yet amid reports that Johnson could delay step four of the road map by two to four weeks.
Foreign secretary Dominic Raab told the BBC’s Andrew Marr Show that ministers would be looking at whether vaccinations have “broken the link” between rising cases and rising hospitalisations, “not just severed or weakened it”.
But scientists advising the government have said they now expect a delay.
Professor Stephen Reicher, a member of the Scientific Pandemic Insights Group on Behaviours (Spi-B) which advises the government, told Times Radio: “I think we’ll hear a delay, because all the data now points that way.”
Cambridge University epidemiologist Raghib Ali, who advises the government on Covid and ethnicity, told Sky News: “I expect the prime minister to say that unfortunately a delay is needed to make sure that we don’t get to the situation again where the NHS is unable to provide care to all its patients.”
He went on: “Hospitals are extremely busy at the moment, the emergency departments last month were the busiest they have been for years because of the huge backlog of patients that didn’t come in during the previous waves.
“Even a relatively small increase in hospital admissions from Covid will have a significant impact on all our non-Covid patients.
“We really can’t afford for those people to suffer any more; they have already suffered enough over the last 18 months.”
Reicher meanwhile warned there was a risk that the country could go “backwards”, as he called on the government to provide more financial support to help people self isolate to stop the spread of the virus.
“In a situation where things are getting worse we don’t know how much worse they’re going to get. We don’t know how many people are going to get seriously ill,” he said.
“There’s still a lot of damage that can be done, therefore it makes good sense to pause.
“I think pausing not moving forward is not enough when things are getting worse and we should be thinking about all sorts of measures, not further restrictions, not lockdown, but the basics that we’ve never got right.
“There are all sorts of things we should be doing better to lower the level of infections to make sure we’re not going backwards.
“The real issue now isn’t should we go forwards … it’s how do we stop ourselves going backwards?”
Scientists now estimate that 96% of all new cases of coronavirus are attributed to the Delta variant.
The latest figures from Public Health England (PHE) show there have been 42,323 cases of the Delta variant confirmed in the UK, up by 29,892 from the previous week.
It estimates the strain is 60% more transmissible compared with the previously dominant Alpha, or Kent, variant, and that cases are doubling every four-and-a-half days in some parts of England.