Disgraced footballer Joey Barton has been denied early release with an electronic tag and must serve up to another month in jail, sources have confirmed. Barton, 25, and his club Newcastle, had hoped he would be freed early next week and given a tag forcing him to observe a curfew. But the midfielder has been deemed not to fit the right criteria for early release as he is a violent offender and committed his last offence while on bail. It will come as a crushing blow for Barton - and his club - as he will spend more weeks locked up and miss most of the crucial pre-season. Barton is currently being held in Manchester's Strangeways jail - home to some of the UK's most violent drug dealers and gangsters. The Huyton-born footballer pleaded guilty to assault and affray at Liverpool Crown Court after punching a man to the ground and pummelling his victim up to 20 times with his fists in an attack caught on CCTV in the city centre last December. He was jailed for six months on May 20, but it was thought he would only serve one third, or eight weeks and be released early, around July 15, with an electronic tag to monitor his movements. But probation and prison officials, in line with Ministry of Justice guidelines, have now ruled Barton was not suitable to be released early with a tag given his past crimes. The Ministry of Justice would not comment on the terms of the player's release. However sources confirmed he was denied a tag and must now serve another four weeks in jail. He can now expect to be released in early August. Barton is also serving a four-month jail sentence, suspended for two years, after a separate conviction for a 'ferocious' training ground attack on former Manchester City colleague Ousmane Dabo, which left his victim unconscious and bleeding. He was also ordered to complete 200 hours of unpaid community work and pay £3,000 compensation to Dabo and court costs of £3,430. He was on bail over the Dabo incident when he got involved in the fight outside a McDonald's restaurant in Liverpool city centre last December. The court heard the player, who had been on a night out with friends and family and had consumed ten pints of lager and five bottles of lager, led his group into the McDonald's for food at about 5am on December 27. The party became involved in a confrontation with a group of youths and outside the restaurant the rows continued, and Barton was caught on CCTV knocking an unidentified man to the ground. He then straddled the man and punched him up to 20 times. Moments later, the player attacked 16-year-old Jordan Spencer, punching him in the mistaken belief the youth had assaulted his cousin. The punch broke a number of Mr Spencer's teeth and, as it took place, a member of Barton's group was shouting: 'Stamp on him, Joey, stamp on his head.'