Bradford and Oldham are on a Government "watch list" of places in which local lockdowns could be required if more targeted measures fail to get to grips with fresh coronavirus spikes, The Telegraph understands.
After Leicester, on Tuesday, became the first city in the UK to have measures reimposed, there is mounting concern over areas in the Midlands and north of England with large minority populations.
Whitehall insiders confirmed that Bradford, the city with the second highest rate of infection after Leicester, was being closely monitored, along with a number of other towns deemed at risk.
According to Public Health England data, Bradford, Barnsley, Rochdale and Oldham are the four areas after Leicester with the highest number of cases.
It is thought some of the UK's most diverse towns and cities are particularly vulnerable to flare-ups due to higher numbers of households with multiple generations living under one roof.
Poverty, language barriers, higher levels of non-compliance with lockdown measures and potential outbreaks in food processing plants and factories are also believed to be contributing factors.
According to figures from the NHS and Public Health England, infections have also risen in Medway, in Kent; the London boroughs of Hammersmith and Fulham and Ealing, and Lanarkshire and Dumfries and Galloway, in Scotland.
While there are currently no plans to impose further local lockdowns on other Covid-19 hotspots, which remain behind Leicester’s trajectory, ministers are carefully studying daily testing data compiled by the Joint Biosecurity Centre in case the situation worsens.
"There are a number of different places that people are looking at," one source said. "We are very aware of potential issues. It's only been in the last week that we've seen Leicester take off."
Another source said: "Obviously we are alerted to parts of the country where there are peaks. Anywhere that appears out of the ordinary, we are keeping an eye on."
It comes after Matt Hancock, the Health Secretary, confirmed on Tuesday that ministers were "of course" looking at similar places to Leicester, although he pointed out that the city's infection rate was three times higher than Bradford.
Separately, Jeremy Hunt, Mr Hancock's predecessor, told BBC Radio 4’s Today programme that Leicester was unlikely to be a "one-off occurrence''.
"We know that the NHS Test and Trace process was going to take until the end of June before it could fully get local public health officers and local authorities on board and co-ordinated with their efforts," he said.
"We're now at that point, so I think there will be things when it comes to other cities and similar situations that happen more smoothly. We have shown that we're prepared to react quickly and decisively when there is an outbreak, and let's hope we can get through this in Leicester quickly."
Testing figures compiled in a recent PHE report showed that Bradford, Barnsley and Rochdale had all recorded at least 45 new cases per 100,000 people in the seven days up to June 21.
PHE said cases were highest in the north of England and there had been increases outside hospital settings in Yorkshire and the Humber during the past fortnight. Doncaster has also seen a worrying spike in new cases, from 11 in the week to June 19 to 32 last week.
Across England, 36 cities and counties are seeing fresh spikes in cases, although some of these increases remain in the single digits.
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