Coronavirus cases are doubling about twice as fast in the North West, Yorkshire and the West Midlands as for the whole of England, according to the largest Covid-19 study of its kind.

Experts behind the React study said the rate of growth of the epidemic across England has slowed in the last month, but the country was now at a “critical point in the second wave”.

They warned that current measures such as the rule of six and restrictions in the north of England will not be enough to bring the epidemic under control.

They said “further fixed-duration measures should be considered to reduce the infection rate and limit the numbers of hospital admissions and deaths from Covid-19”.

The report looked at Covid-19 swabs from 174,949 volunteers tested across England between September 18 and Monday this week.

It found cases are doubling every 29 days in England, much slower than the 13 days estimated for the period mid August to early September, resulting in a national reproductive rate (the R number) of 1.16.

At a regional level, the team estimated cases are doubling much quicker – every 17 days in the North West, 13 days in Yorkshire and the Humber and 14 days in the West Midlands.

However, they said the doubling time may be as low as seven days in Yorkshire and the West Midlands, and every nine days in the North West.

Across England, about one in 170 people currently have the virus and there are approximately 45,000 new infections each day, the report continued.

It pointed to “high prevalence” of Covid-19 across England and said “prevalence has increased in all age groups, including those at highest risk”.

The highest prevalence of the virus is among 18 to 24-year olds, but prevalence among anyone aged 65 and over has increased eight-fold since mid August to early September, to 0.33%, the report said.

It also found that at least half of people with Covid-19 will also not display symptoms on the day of testing or in the previous week.

The experts concluded: “Improved compliance with existing policy and, as necessary, additional interventions are required to control the spread of (coronavirus) in the community and limit the numbers of hospital admissions and deaths from Covid-19.”

The report put the R value in the North West at 1.27, at 1.37 in Yorkshire and the Humber, and 1.33 in the West Midlands.

For London, the team estimated an R value of 0.97 and suggested the high number of cases seen in the first wave may have had an effect on the capital.

Professors Steven Riley and Paul Elliott, from Imperial College London, led the study, which included colleagues from the University of Oxford and Lancaster University.

Prof Riley said there was evidence of “continued growth and possibly rapid growth” in regions such as the North West, Yorkshire and the West Midlands but the key message across England was that “prevalence is high”.

He added: “Prevalence is going to continue to go up unless either compliance with the messaging improves, or additional measures are introduced that are supported by the general public.

“There is a very strong epidemiological case for trying to reduce the transmission right now.”

Prof Riley said prior exposure to the virus among people in London could be contributing to its lower R rate.

He said a degree of immunity “will be making some effect, but it’s not clear as to what degree”, adding that “on average across London, the total amount of immunity is quite low”.

Asked by reporters how far England was off the pandemic peak seen earlier in the year, Prof Riley said: “If things don’t change and the patterns that we describe continue, then in a relatively short period of time we will get back to comparable prevalences in some parts of the country.”

He said the data supported further restrictions in the north of England “sooner rather than later”.

Professor Elliott said the combination of the current restrictions, including the rule of six, was “possibly having some effect, but not enough to turn down the virus”.

The report comes as separate data from the Office for National Statistics (ONS) estimates that 224,400 people in England had coronavirus between September 25 and October 1, equating to about one in 240 people.

Katherine Kent, co-head of analysis for its Covid-19 infection survey, said: “We’ve seen another striking increase in the number of people testing positive for Covid-19 across England in this week’s figures.”

Further data from the Covid Symptom Study (CSS) app run by King’s College suggests there are currently, 21,903 daily new symptomatic cases of Covid in the UK on average.

Its data points to more than five times more cases in the North compared with the south of England.