The leader of Blackburn with Darwen Council has said it is "sensible not to relax" lockdown restrictions, as the rate of Covid-19 cases in the borough shot up.
Councillor Mohammed Khan urged the community to "keep up the momentum" in combating the disease as 122 new cases were recorded in the seven days to July 20.
Public Health England has upgraded Blackburn with Darwen to an "area of intervention" following the increase, which was the highest at local level.
PHE defines such areas as those "where there is divergence from the measures in place in the rest of England because of the significance of the spread, with a detailed action plan in place, and local resources augmented with a national support".
"We are very grateful to our communities for working with us," said Mr Khan.
"The increase in testing is helping to ensure that we are heading in the right direction with a reduction in positive cases and hospital admissions.
"We need to keep up the momentum with our strong prevention work so we agree it's sensible not to relax the easing of restrictions at the moment to stop the spread.
Mr Khan added the decision to delay the reopening of council leisure facilities would run alongside new "localised prevention measures".
We feel that accelerating our control measures in this way will assist us to move out of having higher Covid rates even faster - we are grateful for the Government's help in our local plans on this.
The rate of cases in Blackburn with Darwen has jumped from 49.7 cases per 100,000 in the seven days to July 13 to 81.9 in the seven days to July 20.
Luton, in Bedfordshire, has also been upgraded to an "area of intervention", though its rate of cases has gone down.
NHS Test and Trace chief Baroness Dido Harding said there were still concerns surrounding northern towns including Blackburn, Bradford and Leicester.
She told the BBC there were "a number of areas in the North West that we are working really closely with".
Other towns and cities on our areas of concern, or areas that are receiving enhanced support, would be places like Blackburn, also Bradford - who we saw increase but have now come down from being in our 'enhanced support' category to being in our 'area of concern' category.
Lady Harding added there were particular concerns about coronavirus spreading in South Asian communities in England.
"We are all learning what makes different communities, different professions, different parts of the country more vulnerable," she told the broadcaster.
"I don't think there's a simple answer to say why one place and not another.
"There are a mix of things - certainly we are seeing a very high prevalence in the South Asian community across the country."