20 places in England have been listed as at risk of a new outbreak of coronavirus on a leaked memo from Public Health England.

The list, topped by Leicester which has gone into a local lockdown, categorises places on how much risk they are at – from red for the most serious through amber to green.

The areas have been flagged as needing increased monitoring and support – with additional testing being provided in some places.

The Public Health England memo says Sheffield, Bradford and Kirklees need “enhanced support” while Bedford, Barnsley, Rotherham, Oldham, Rochdale and Blackburn with Darwen are noted as areas of “concern”.

The report, obtained by The Observer, outlines the level of concern based on “daily exceedance” of the virus.

Five areas – Blackburn with Darwen, Sheffield, Bolton, Knowsley and Carlisle – are rated red for “daily exceedance”.

Three more areas, Rochdale, Oldham and Northampton, are rated amber. Testing access is being increased in some of the areas, including Bradford.

According to the Observer, the document says “these areas are currently under investigation by the local public health protection teams”.

A Department of Health and Social Care spokesman said: “Throughout the pandemic, we have been transparent about our response to coronavirus and are always looking to improve the data we publish, including the way we update testing statistics.

“The list of the ten local authorities with the highest weekly incidence of coronavirus is already publicly available in PHE’s weekly surveillance report.

“All councils in England now have the ability to access testing data, right down to an individual and postcode level. If councils feel they require more assistance with data, of course, PHE is able to help them.”

20 areas in the leaked report in full

Area (Daily Incidence per 100,000 population, 7-day average to July 4).

1. Leicester (16.3)

2. Kirklees (4.9)

3. Bradford (4.7)

4. Blackburn with Darwen (4.5)

5. Oadby and Winston (4.0)

6. Rochdale (4.0)

7. Ashford (3.8)

8. Folkestone and Hythe (3.7)

9. Blaby (3.3)

10. Oldham (3.2)

11. Rotherham (3.2)

12. Barnsley (3.1)

13. Bedford (2.8)

14. Northampton (2.5)

15. Sheffield (2.5)

16. Bolton (2.4)

17. Hinckley and Bosworth (2.3)

18. Kettering (2.3)

19. Knowsley (2.3)

20. Carlisle (2.2)