Despite the assurances of his club manager Kevin Keegan that Barton is a changed man, Judge Henry Globe, who described the player as “aggressive and disgraceful”, sent him to prison.

Newcastle are currently considering the implications of Barton’s sentence, which also included four months concurrently imposed for affray and £2,500 compensation order to his 16-year-old victim.

“Newcastle notes the sentence passed to Joey Barton at Liverpool Crown Court,” said a statement.

“The club is considering the verdict and will be making no further comment at this moment.”

Barton, cousin Nadine Wilson, 27, and brother Andrew Barton, 20, were captured on CCTV in a number of violent incidents in Liverpool city centre on December 27 last year.

It took place as Barton was on bail for an alleged assault of former Manchester City team-mate Ousmane Dabo, 31, and a separate criminal damage offence.

At around 5am the player, who had consumed 10 pints of lager and five bottles of lager, went into a McDonald’s restaurant with his brother and Wilson.

The court heard Wilson became involved in a confrontation with a group of youths and the row continued outside the restaurant, with Barton caught on CCTV knocking an unidentified man to the ground.

He then straddled the man, and punched him four or five times as Wilson threw food at the victim before Barton punched him up to 15 times more.

Minutes later, the player attacked 16-year-old Jordan Spencer, punching him in the mistaken belief the youth had slapped Wilson. The punch broke a number of Mr Spencer’s teeth.

Ian Harris, prosecuting, described the incident as “violent and cowardly”.

The court was told the Barton brothers had been goaded by remarks about their half-brother Michael, who is serving life for the racist murder of Anthony Walker in Huyton, Merseyside, in 2005.

Stuart Driver QC, for Barton, said his client had been subjected to “truly obscene” references to his half-brother by other city centre revellers.

He said: “Minutes of build-up led to a few seconds of violence.”

In his character reference, Keegan described how Barton was a changed character from when he knew him while Manchester City manager.

He said: “Had I been asked to give character evidence for him then, I probably would not have been able to do so.

“But he has taken stock of his life, he is more thoughtful in his actions and character. He is a far more responsible individual.”

Peter Kay, of the Sporting Chance clinic in Hampshire which has been supporting Barton since January, said the player had an alcohol problem.

Judge Globe told Barton: “Without doubt, the most serious of the three offenders is you.

“You acted in an extremely violent and aggressive manner.

“You have a high profile as a footballer and you know that draws attention to you. Yet you drank to excess and behaved in an aggressive, disgraceful manner.”

Wilson, of Childwall, Liverpool, was given a six-month sentence for ABH and two months for affray, suspended for two years.

She was also given a 12-month supervision order and instructed to carry out 12 months unpaid work.

Andrew Barton, also of Foxbank Close, Widnes, was given a four-month sentence for common assault, suspended for two years, and a 12-month supervision order.