Drinkers have experienced a first full night of extended licensing hours in England and Wales, although little disorder has been reported by police.
The effect of the change is likely to be tested at the weekend
Senior officers say the weekend will be the real test of the new laws' effect on behaviour, but the Police Federation predicted arrests would increase.
Ministers say the law gives police more powers to tackle alcohol-related crime.
Some 40% of the 190,000 licensed premises varied their licences, with 1,008 able to serve alcohol all day.
Around a third of the 24-hour licences were for pubs, bars and nightclubs, and another third for supermarkets, a survey by the Department for Culture, Media and Sport of 336 of the 378 licensing authorities found.
Jan Berry, chairwoman of the Police Federation - which represents rank-and-file officers - said: "We understand that the majority of drinkers will be responsible, but experience dictates that the behaviour of the minority will result in a large increase in alcohol-related disorder."
This would "add to the pressure on our members and... put a further drain on already stretched resources", she said.
Metropolitan Police Commissioner Sir Ian Blair, Britain's most senior officer, has also expressed concern that his force will be "stretched", particularly in the early hours of the morning.
Professor Ian Gilmore, of the Royal College of Physicians, predicted alcohol consumption would go up 10% with extended opening hours.
"We will see the country drink more - we could probably close our A&E units at 9pm if it wasn't for alcohol," he told GMTV.
But Culture Secretary Tessa Jowell said the laws would give responsible drinkers "more freedom", while also giving police "the powers that they need to tackle the problem we have as a country of alcohol-related crime and violence".
BBC research suggests that around one third of all licensed clubs, pubs and shops in England and Wales will be able to open for longer under the new laws.
A BBC News 24 survey found:
- There have been 60,326 extensions in hours for selling alcohol - this is from 301 of the 375 authorities, so the final figure will be higher
- 1,121 establishments will have 24-hour licences and of these 359 are pubs or clubs
- South East England has the largest number of approved licences - 10,500
- Some 5,200 extensions have been approved in London - but just 14 pubs or clubs can open for 24 hours
- More than 150 pubs or clubs in the south and west of England gained 24-hour licences, with just eight in the West Midlands.