Pub-goers are being urged to remember the importance of social distancing ahead of the second weekend of trading since the lifting of coronavirus lockdown measures in England.
Crowds on Old Compton Street in London's Soho last Saturday night were described as being "out of control," while alcohol-related anti-social behaviour caused some establishments to close early in Nottinghamshire.
Authorities are keen to avoid similar scenes this weekend.
Mayor of London Sadiq Khan has told people to "stay safe" and wear a face mask when "out and about".
Alongside a video on Twitter, in which he is wearing a mask, Mr Khan wrote: "Enjoy supporting your local businesses this weekend, but stay safe – lives depend on it.
"This includes wearing a face covering on public transport, in shops and where you can’t keep a social distance."
Many of those on Old Compton Street last weekend were not wearing face coverings, with one onlooker estimating that there was between two and three thousand people on the street.
Westminster City Council said venues would be served clear reminders of their responsibilities and have been asked to implement a "no seat, no service" policy.
Councillor Matthew Green, cabinet member for business and planning, said: "Last weekend we saw a vast reopening of London's most famous hospitality areas, with a large majority showing a safe and successful example of the new normal for the city’s bars, cafes, and restaurants.
"At the same time, we saw isolated instances of crowding in some of our busier areas.
"This is something that cannot happen again as we must ensure the safety of the public as a result of the Covid-19 pandemic."
Elsewhere, Greater Manchester Police Superintendent Chris Hill said last weekend ran smoothly - with just three premises voluntarily closing early following safety advice from officers and the local authority.
He said: "As we approach another weekend, one that promises slightly sunnier weather, I want to remind the public of the importance of continuing to social distance and respect others - the guidelines and restrictions still in place are paramount to preventing a second spike and not undoing the hard work done so far by everyone to minimise the spread of the virus."
Sacha Lord, night time economy adviser for Greater Manchester, said this weekend will likely see even more venues opening their doors, adding: "I also expect the industry to be under more pressure this weekend – a combination of better forecasted weather and great consumer confidence means we can safely anticipate more customers and therefore more pressures to maintain those safe standards.
"I want to appeal to the sector to keep its standards high. To the public, please stay local and boost nearby businesses, and please continue to respect the safety measures that are in place."
Meanwhile, Merseyside Police expressed concern ahead of the weekend, writing on Twitter: "It’s concerning to see a rise in COVID19 cases in South Liverpool – stay safe this weekend and remember to follow public health guidelines."
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