The 25-year-old was due to go on trial at Manchester Minshull Crown Court over the incident, but changed his plea shortly before the scheduled start.

Barton admitted one charge of assault occasioning actual bodily harm to Ousmane Dabo when they were playing colleagues at Eastlands.

It is the third time Barton has been in court in 2008, but his bad behaviour stretches back more than four years.

In April 2004 he stormed out of Eastlands before kick-off after being axed from the side to face Southampton and in a 2005 pre-season friendly sparked a mass brawl in a game against Doncaster.

A Christmas bash for Manchester City players that December saw him stub a lit cigar into the eye of young team-mate Jamie Tandy. He was fined six weeks' wages by City.

In May 2005 he broke the leg of a 35-year-old pedestrian while driving his car at 2am in Liverpool city centre and the following month was involved in a spat with a 15-year-old Everton fan at City's team hotel in Bangkok. Again he was fined by City.

The bad blood with Everton fans continued in 2006 when he dropped his shorts in the direction of home fans at Goodison Park. He was fined and warned by the FA for his conduct.

In February last year was arrested on suspicion of assault and criminal damage in an incident involving a taxi driver. Three months later came the fight with Dabo, and a month after that he was sold by City to Newcastle Utd for £5.8million.

Barton - whose victim Dabo was in court to hear him plead guilty - will be sentenced on Tuesday.