Violent crime increased in Birmingham following the introduction of 24-hour drinking, a Home Office study has shown.
But the change to the licensing laws also coincided with fewer complaints of drunk behaviour in the city centre.
The study, which painted a mixed picture, was published as the Government insisted the "widespread problems" feared by many had not materialised.
Culture Secretary Andy Burnham said 24-hour drinking was here to stay. But critics claimed the Government's plan to reduce drunken crime by creating a Continental-style "cafe culture" had been a failure.
Mr Burnham was announcing the results of a Government review of the Licensing Act 2003, which came fully into force in November 2005.
It looked at the effect of late licences in five towns and cities - Birmingham, Guildford, Nottingham, Croydon and Blackpool.
In the first 12 months of the new laws, crimes of violence against the person rose by 9.4 per cent in Birmingham at weekends. Violent crime also rose by 4.7 per cent on weekdays. This gave an overall increase of 6.7 per cent, up from 3,639 incidents a year to 3,884.
The study, produced for Ministers by academics at Kings College, London, said this was "not statistically significant".
However, the study also found that incidents were spread out throughout the night and early morning and no longer concentrated in two or three hours, potentially making the job of police easier.
And it found that people who lived and worked in the city centre saw drunken and rowdy behaviour as less of a problem following the reforms to the licensing laws.
There are 76 premises in Birmingham with 24-hour licenses to sell alcohol, including 15 pubs, bars and nightclubs, and 13 shops.
The drinking capital of Britain is Blackpool, where 871 24-hour licenses were issued.
In a statement to the House of Commons, Mr Burnham admitted some parts of the country appeared to have suffered ill effects because of the change to the law.
But he claimed local authorities were failing to use the powers they had been given to clamp down on violence and anti-social behaviour. He said: "Whilst crimes involving violence may have reduced over the evening and night-time period, the evidence also points to increases in offence, including violent crimes, reported between 3am and 6am."
Mr Burnham said the Government would introduce new measures to punish pubs and bars associated with violence.
The Government is to produce a "ranking" of areas based on the risk their bars and off-licences pose to "crime and disorder, public nuisance and children".
Police and local authorities will then be able to use this information to identify "hotspots", where licences may be withdrawn "wholesale", according to Mr Burnham.
Conservatives claimed the report showed that 24-hour drinking had been a disaster.
Shadow home secretary David Davis said: "The damning evidence against the Government’s 24-hour drinking policy is overwhelming and comes from all sides: from the police, local authorities, statistics on hospital admissions and the Home Office itself"
He added: "As for the Government’s proposals, they are a hastily cobbled together mix of reheated announcements that have not even been properly enforced in the past two years, or a blatant attempt to rip off existing Conservative policy."
Liberal Democrat Culture spokesman Don Foster said: "Ministers told us the Act would reduce drunken disorder, binge drinking and underage drinking.
"In reality we’ve seen a rise in violent crimes late at night, too many licensed premises still selling to children, and soaring alcohol related A&E admissions."