Police were called and two men arrested following the incident in the early hours of Monday morning (local time).

Barton, 29, voluntarily left the scene, which took place outside the Garlands nightclub in the city's centre.

"We have arrested two men following reports of a disturbance in Liverpool city centre in the early hours of this morning," Merseyside Police said in a statement.

"Officers were called at 5.30am following reports of an altercation outside of a nightclub.

"On arrival they found a 29-year-old man who had sustained some injury to his face.

"The man left the scene voluntarily. Two 21-year-old men were arrested at the scene for a public order offence and they are currently in police custody."

Barton took to Twitter tonight to claim he was the victim but had suffered only minor injuries.

" I got sucker punched in the back of the head," he tweeted. "Not injured as reported just a small bruise on rear of head/ear.

"I've had worse. Life goes on! Thanks for the concern. Have a good day people."

Barton is no stranger to controversy.

The former Newcastle United player received a 12-match ban from the Football Association following his sending off against Manchester City in the final match of the 2011/12 English Premier League season.

In May 2008 he was sentenced to six months in prison after pleading guilty to assault, and avoided previous jail terms after separate assaults on a fan and a team-mate in 2006 and 2007 respectively.

The later incident resulted in then-Manchester City colleague Ousmane Dabo suffering a detached retina.