Pubs, restaurants and cafés are the sources of one-fifth of COVID-19 infections, according to medical experts.
Pubs contributed to 9% of cases but hospitality venues altogether were at 20%, deputy chief medical officer Jonathan Van-Tam said on Friday.
He briefed MPs and peers amid calls from some politicians to see the evidence behind giving pubs a 10pm curfew.
A scientist advising Boris Johnson claimed he had never heard the curfew plan discussed before it was announced this week.
Health minister Lord Bethell has suggested “late-night intimacy” is one reason for the government’s decision to introduce the earlier closing time for hospitality venues.
In a debate on COVID-19 regulations, he said establishments that follow the rules are unlikely to “present a threat” but he added that not all do.
Earlier on Friday, former Labour cabinet minister Lord Blunkett said the “elephant in the room” was whether the Eat Out to Help Out scheme might have driven a spike in infections.
He added: “Infection rates during August rose and admissions to hospital by the end of August had started to rise.
“Has this any correlation with the Eat Out to Help Out, which economically was incredibly successful, but might actually have contributed to where we are today.”
Independent peer Baroness Wheatcroft called for greater clarity from the government and claimed the public was confused as to why you could meet people at pubs or restaurants but not at home in locked-down areas.
She said: “I listened to the deputy chief medical officer Professor (Jonathan) Van-Tam and he made it very clear that the hospitality industry did help fuel the spread of the disease.”
Independent peer Baroness Uddin warned restaurants faced a “massive hit” due to the 10pm curfew.
She said: “The hospitality industry once again will take a massive hit just as many, including in the British curry industry, felt some hope of survival.”
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