Sam Allardyce made the plea to his old club following the news this week that Barton's future is in doubt following his latest criminal conviction.

The 25-year-old midfielder was given a four-month suspended sentence after admitting an assault on former Manchester City team-mate Ousmane Dabo.

He is already serving a six-month sentence for affray and assault following an early hours incident outside a McDonald's in his native Liverpool.

Allardyce paid Man City £5.8m for Barton a year ago, making him one of the first signings of his brief United reign.

Newcastle have lost patience with the midfielder and could even sack him, but Allardyce - who was succeeded by Toon legend Kevin Keegan - says the club should do their utmost to keep him.

Allardyce believes taking the player out of football could have a drastic affect on his personal life.

"If Newcastle sack him, then it will be another punishment and defeat the objective of Joey trying to put things right and become a better person," he wrote in his column in The National.

"It could also be dangerous to take away football from him. He is a complete football man. His life revolves around it, there's nothing else.

"Without it he could re-offend and, even worse, go into a depression.

"We've had people in the past committing suicide because they could not cope with life after professional football.

"If Newcastle keep Joey, this is the last chance for him.

"When I signed Joey I knew about his troubles. I had asked about him and I asked him directly.

"He told me he was working on his problems, like alcohol, and getting expert help at the Sporting Chance clinic.

"There is no question he has ability, but that won't make any difference if he cannot control himself off the pitch.

"He has to gain everyone's trust again - not only as a footballer, but also as a person."