Opponents have accused the British government of putting lives at risk by failing to share information about local coronavirus outbreaks with affected areas.
The government has reimposed a lockdown on the central England city of Leicester after a spike in cases.
Several other communities are striving to contain local outbreaks and avoid having to bring back similar restrictions just as many parts of the country begins to open up.
Leicester, a city of 300,000, has been forced to shut schools, close non-essential shops and ban all but essential travel, days before the rest of England takes further steps out of lockdown with the reopening of restaurants, pubs and hairdressers on Saturday.
Officials in Leicester, 160km north of London, say they weren't given detailed data on the scale and location of local COVID-19 clusters for almost two weeks after the rise in cases was identified, leaving them scrambling to stem the spread of the virus.
Labour leader Keir Starmer said the government had publicly mentioned an outbreak in Leicester on June 18 but didn't give local authorities full data for another week, and didn't impose a lockdown until 11 days later.
"There was a lost week while the virus was spreading," Starmer said in the House of Commons.
He demanded a "cast-iron guarantee" that no other authority would be put in the same position.
The government said "postcode-level" data has been available to local officials across the country since last week, though it didn't explain why it had been unavailable earlier.
Officials are trying to pinpoint the seat of the Leicester outbreaks, with attention focused on the city's garment factories and food-processing plants.
Potato crisps maker Walkers, one of the city's main employers, said 28 members of its 1400-strong workforce had tested positive for the coronavirus.
The company said the number reflected "the situation in the local community" and coincided with an expansion of testing in the city.
The UK's official coronavirus death toll rose by 176 on Wednesday to 43,906 - the highest in Europe and the third-highest in the world after the US and Brazil.
But the country's infection rate has been falling and Britain is gradually easing lockdown restrictions imposed in March.