Test and Trace did not provide details of more than 700 positive cases to eight local authorities in England, according to a BBC report.
The BBC said a report concluded the rapid spread of Indian strain within its boundary was “exacerbated by the sporadic failure of the national Test and Trace system”.
Surge testing and vaccinations have been taking place in Blackburn in Lancashire, along with a number of other impacted areas in the UK, after cases of the B1617.2 variant increased.
Downing St has denied the Test and Trace delay helped contribute to the spread of the Indian variant.
The Prime Minister’s official spokesman said: “The NHS, as I understand it, has contacted over 10 million people since the start of the pandemic and this has had a significant impact in breaking chains of transmission.
“In this specific instance, all positive cases were contacted and told to self-isolate for 10 days.
“As you know, there was a short delay when asking some of those positive cases to provide details of individuals they had contacted since contracting Covid.”
NHS Test and Trace - for which £37bn has been set aside by the Government- identifies people who have been in close contact with someone who has caught Covid.
Labour said the suggestion that local public health officials had been “left in the dark” over their case numbers “beggars belief”.
Labour shadow health secretary Jonathan Ashworth said: “This is deja vu and echoes the mistakes made last year with Boris Johnson’s ‘whack-a-mole’ approach.
“Ministers need to explain what’s gone wrong and provide local health directors with all the resources they need to push infections down.”