Bolton Council's leader David Greenhalgh said the area's high infection rate is linked to pubs and a "cohort of people" who refused to follow guidance, including the man who went drinking with friends instead of quarantining for 14 days when he returned from abroad.
The man was asymptomatic at the time, but developed symptoms after the pub crawl which "led to a large number of individual transmissions".
Mr Greenhalgh told the BBC: "We had somebody who did not adhere to quarantine, did not stay the 14 days, literally went on a pub crawl with a number of mates.
"From that incident which took place over a weekend - (they) visited a number of premises - led to a large number of individual transmissions from that one person which you can imagine then is like holding back the tide because he then became symptomatic two days after they had all gone on this pub crawl.
"He was positive-tested the following day.
"That is four or five days where all the people he was in contact with have been going about their normal day-to-day business."
The revelation comes as other councils urge the Government to give them more powers to shut down premises where rules are being broken.
Enfield Council leader Nesil Caliskan, one of those campaigning for more powers for councils, also said: "We are incredibly limited because the legislation in places doesn’t allow us to give warnings or go in and close venues so the Local Government Association and local authorities across the country are calling on the Government for additional powers to allow us to do that and I think that will be crucial in coming weeks.
“If we don’t see a lockdown we will need to be able to see councils take a tougher stance in order to be able to ensure people keep each other safe and venues are adhering to social distancing laws."
Police chiefs have warned that officers will be out in force this weekend and urged people to follow social distancing rules.
Greater Manchester Police said they had already taken action after discovering that a gazebo had been erected in a garden for a wedding party.
The force wrote in a tweet: "Officers prevented the illegal gathering before restrictions were breached."
Kent Police said there would be an increased presence in "key areas" around the county, as Covid-19 remains a "real and deadly threat".
While the Metropolitan Police in London have called on those in the capital to "continue to act responsibly" as warm weather is predicted to hit the area.
The force has announced it plans to continue to increase patrols in public spaces, disperse gatherings of more than six and remind the public of fines for breaching coronavirus guidelines.
People who flout the new rules for gatherings of six, which applies to both indoor and outdoor settings, face fines of up to £3,200.
Earlier this month a 23-year-old man from Bolton was fined £1,000 for failing to self-isolate after returning from a holiday in Ibiza and hosting a house party.
Bolton is subject to tougher measures than the rest of England, with hospitality venues only allowed to operate as takeaways and ordered to shut by 10pm.
On Saturday the Huffington Post website reported that Mr Khan has warned the PM that the measures should come into effect as early as Monday.