The London transport system was heavily disrupted overnight as thousands of revellers held an unauthorised "drinks party" on underground trains before an alcohol ban went into effect.

The key Circle Line which serves some of the capital's most exclusive districts was shut down as thousands of people gathered for a booze-up on Tube trains after being rallied by social networking websites.

"There are problems on the Circle Line and it has been stopped," a London Transport Police spokesman said.

David Mudkips, a 25-year-old computer programmer, described the experience on one of the trains packed with revellers as: "Like rush hour but fun. There were people's sweaty armpits in my face but I didn't care because I was drinking."

Police made at least six arrests as the behaviour of the crowds became increasingly boisterous.

Thousands of people had signed up for the party on Facebook sites with names like "The Booze Tube" and "One Final Tube Booze Party".

From today, anyone caught drinking from, or even carrying, open containers of alcohol will be ejected from trains and buses.

The alcohol ban will apply to buses, underground Tube trains, trams and stations.

Newly elected London Mayor Boris Johnson introduced the alcohol ban in one of his first acts in office.

Johnson said: "I firmly believe that banning the drinking of alcohol on London's public transport will create a better travelling environment for all Londoners and that if we drive out anti-social behaviour and so called minor crime then we will be able to get a firm grip on more serious crime."

The ban has been criticised by the railworkers' union RMT as another burden on its overworked members.

The union's general secretary Bob Crow warned it could put staff in greater danger of assault.

"Violence against Tube staff is already a major problem, particularly from people who have been drinking, but now our members will be expected to approach people drinking and stop them or even remove them from the train or station," he said.

However, Don Shenker from Alcohol Concern said the ban "sends a strong message that public drunkenness is socially unacceptable and will support both the public and transport staff".

"Public drinking and the behaviour sometimes associated with it can, and does, deeply affect people's ability to enjoy public spaces," Shenker said.

Tackling crime, particularly serious violence among young people, was one of the main planks of Johnson's election campaign and he has already vowed to put it at the forefront of his mayoralty.

AFP/Reuters