Ministers need to act early to counteract rising Covid infections, the government’s scientific advisers have said while suggesting that failure to do so could mean harsher interventions will be required this winter.

On Thursday daily new Covid cases in the UK exceeded 52,000, the highest since July. Figures from the Office for National Statistics released on Friday show that about one in 55 people in England had Covid-19 in the week ending 16 October, a level last seen in mid-January, and infection levels had increased from the week before in all age groups except 25- to 34-year-olds, where the trend was unclear.

The government has repeatedly said it is not yet introducing its “plan B”, a suite of “light-touch” measures such as advice to work from home, compulsory face masks in some settings and the introduction of vaccine passports.

But documents released by the government’s Scientific Advisory Group for Emergencies (Sage) on Friday show warnings from experts that if action is not taken rapidly as cases rise, harsher measures may be needed later.

“In the event of increasing case rates, earlier intervention would reduce the need for more stringent, disruptive, and longer-lasting measures,” minutes of a Sage meeting held on 14 October record.

The experts say there are many unknowns at play regarding the trajectory of the epidemic this winter, including the rate and degree to which protection from vaccinations wanes, and changes in behaviour. However, the documents from the Sage modelling sub-group add that the earlier measured are enacted, the faster they would be likely to be lifted.

“Similarly, the higher the prevalence and growth rates when measures were introduced, the more rapidly hospital pressures would need to be reduced, and therefore the stricter the measures that would be needed to do so,” the SPI-M-O team says.

The warnings chime with previous comments from the government’s chief scientific adviser, Sir Patrick Vallance, that it should “go hard and go early” in the event of rising cases to avoid a winter surge of Covid.

While the documents stress the importance of vaccination, they suggest plan B measures could be effective.

According to a document from the Sage sub-groups Spi-M, Spi-B and the EMG, “reintroduction of working from home guidance, for those who can, may have the largest impact on transmission out of the potential plan B measures.” The experts add that making the wearing of face coverings mandatory in certain settings is likely to increase their use.

However, the experts are cautious over the use of vaccine passports, noting it is unclear how much impact they would have, and there are concerns around potential harms and unequal impact.

While the Sage documents suggest hospital admissions for Covid are “increasingly unlikely” to climb above levels seen in January, Covid is not the only pressure facing hospitals this winter, with concerns that other respiratory infections, including flu, could place the NHS under extreme strain.

The experts also say capacity to monitor for variants and explore the potential impact on vaccines is crucial. “There should be no complacency around the risk posed by further viral evolution. Emergence of a variant of Delta or a variant from a different lineage that becomes dominant globally is a very real possibility,” the Sage minutes record.

Speaking in a personal capacity, several experts who have advised ministers during the pandemic raised concerns about the government’s current approach.

Dr Ben Killingley, an acute medicine and infectious diseases consultant at UCLH, said he supported taking action. “My personal sense is that we should be increasing precautions and mitigations, plan B. Things are likely to deteriorate with respect to numbers of cases of Covid and other viruses as we move forward. [It] seems policymakers have not learned that you need to act sooner than you would like to, as Patrick Vallance nicely put it. I think that many of my colleagues have the same view,” he said.

Ravi Gupta, a professor of clinical microbiology at the University of Cambridge, agreed. “Plan B should in my personal view be implemented given the escalating and unacceptable morbidity and mortality we are seeing, in addition pressures on the NHS as we approach winter. However, the effects will take a few weeks to see in terms of hospitalisations and deaths.”