The mayor of Liverpool City Region has called for an investigation into whether a Champions League fixture should have taken place in the city in March amid concerns it could have led to a high number of local coronavirus cases.
Liverpool's match against Atletico Madrid at Anfield on 11 March was attended by 52,000 supporters, including 3,000 from the Spanish capital, where a partial lockdown was already in force.
The UK government has defended its decision to allow such events to go ahead before restrictions on mass gatherings were enforced 10 days later.
But Steve Rotheram told BBC Sport an independent inquiry was needed into a potential connection with a surge of cases in Liverpool since.
"If people have contracted coronavirus as a direct result of a sporting event that we believe shouldn't have taken place, well that is scandalous," he said.
"That's put not just those people in danger, but those frontline staff in the NHS and others in their own families that may have contracted it."
The latest figures show 246 people have died with coronavirus in Liverpool's NHS hospitals.
Meanwhile, Madrid is one of Europe's worst-affected cities and Spain has the second-highest number of confirmed infection cases in the world, behind the United States.
"We've seen an increase in the infection curve, and that's resulted in 1,200 people [in Liverpool] contracting Covid-19," said Rotheram.
"That needs to be investigated to find out whether some of those infections are due directly to the Atletico fans. There were coronavirus hot cities, and Madrid was one of those.
"They weren't allowed to congregate in their own country, but 3,000 of those fans came over to ours, and potentially may well have spread coronavirus.
"So it does need looking at, and it does need the government to take some responsibility for not locking down sooner."
The mayor of Madrid has already said the decision to allow the match to go ahead was "a mistake", as has Liverpool city council's director of public health Matthew Ashton.
- 'An interesting hypothesis'
On the day of the match at Anfield, England's deputy chief medical officer, Dr Jenny Harries, said the UK was "following the science and the evidence" in not banning sports events, as other countries had done by then.
"In general, those sorts of events and big gatherings are not seen to be something which is going to have a big effect," she said, despite the World Health Organization urging tougher action by governments that day.
A few days earlier, Prime Minister Boris Johnson had attended England v Wales in the Six Nations at Twickenham.
But while there is no confirmed link between the Liverpool match and any coronavirus cases, on 20 April the government's deputy chief scientific adviser, Angela McLean, said it warranted further investigation, describing it as an "interesting hypothesis."
"The government was saying it was a low risk at the time, but of course just a few days later they completely locked down the country; they banned sports and events and large gatherings," said Rotheram.
"And this could have happened sooner. I haven't got access to the government's scientific advisors, but they would have been asking those questions.
"That's why I think an inquiry needs to tease out just what the government was being advised to do at that time."
On Wednesday, Culture Secretary Oliver Dowden defended the timing of the UK government's ban on mass gatherings.
"Throughout all of this, we have based what we did on the scientific evidence we received both from Sage (Scientific Advisory Group for Emergencies) and from the medical officers," he told MPs.
"There wasn't a case for singling out mass gatherings."
- 'I wish I could go back in time and not go'
A Liverpool fan who fears he may have unwittingly spread the disease at Anfield told the BBC the decision to stage the match was "negligent".
Having returned from a holiday a few days earlier, Ben Johnson felt slightly unwell on the day of the Atletico game and sought medical advice.
As he did not have a cough or fever, he was told to carry on as normal and attended the match.
In the days that followed he developed coronavirus symptoms. He was not tested but says he was on the verge of going to the hospital, before recovering.
"It was obvious it shouldn't have gone ahead," he said.
"It just seems crazy. I wish I could go back in time and not go, and I wish there wasn't the opportunity to go. I just don't understand how it was allowed to go ahead."
Both European football's governing body Uefa and Liverpool have declined to comment.
- Cheltenham 'should have been stopped'
The Liverpool v Atletico match was the last major football game to be played in England, with the season suspended two days later.
There have also been calls for an investigation into whether horse racing's Cheltenham Festival - staged in the second week of March - should have gone ahead. There are concerns it may also have led to a high number of local coronavirus cases, with 251,684 spectators in attendance across the four days.
Professor Gabriel Scally, former director of public health in the south west of England and visiting professor of public health at the University of Bristol, said there "seemed to be" a high number of Covid-19 cases in Gloucestershire.
"I think it's very tempting to link it to the Cheltenham Festival," he said. "Really, from a health point of view, [it] should have been stopped in advance."
Government data shows there have been 972 cases of the virus in Gloucestershire, and 147 people have died.
The postcode neighbouring Cheltenham Racecourse had the highest number of coronavirus hospital admissions in Gloucestershire earlier this month, according to leaked official data.
A number of high-profile attendees have reported symptoms - including West Bromwich Albion player Charlie Austin, comedian Lee Mack and Gold Cup-winning jockey Andrew Thornton.
Cheltenham organisers introduced special hygiene measures for the event, including extra hand-washing stations, and say they had followed clear guidance from the government and science experts.
Dr Sue Smith, senior racecourse medical officer for the festival, has said the hygiene standards were "of the highest level and all measures were taken in accordance with daily updates from Public Health England".