Joey Barton has been made available on a free transfer, Newcastle have confirmed on their official website.
Relations between the club and the outspoken midfielder had already been strained following a breakdown of contract talks over the summer, with Barton taking to Twitter to air his frustrations.
The 28-year-old did so again following yesterday's friendly defeat at Leeds, before saying he would make an announcement on his future at 4pm today.
But the club have pre-empted whatever Barton was going to say by announcing he is able to leave the club a year out from the end of his contract.
A brief statement on http://www.nufc.co.uk read: "Newcastle United can today confirm that Joey Barton has been placed on the transfer list.
"The player has been advised that he can leave the club on a free transfer."
Barton made reference to behind-the-scenes unrest on the social networking site yesterday afternoon, following on from full-back Jose Enrique who was recently fined by the club for accusing them of lacking ambition via his own account.
"If only we as players could tell the fans exactly how it is, without them above fining us lots of money. There will be a time and a place," Barton wrote.
"If it wouldn't effect team morale and cause unrest within the dressing room, am certain Jose's comments would be the tip of the iceberg.....
"And again it would be left to those magnificent fans to pick up the remnants of their once great football club. £hadenoughofcertainpeople.
"If I wanted to leave, I'd just come out and say I want to leave. Things need addressing as am not prepared to go through a relegation again."
In May, Barton's agent Willie McKay said the player would not be offered a new deal with the club, with Barton later Tweeting that they wanted a "'younger, better, cheaper player".
The Liverpudlian has become a fans' favourite in the north east after initially suffering a troublesome start to his life on Tyneside.
After joining for £5.8million from Manchester City in June 2007 he served a 77-day prison sentence after being found guilty of assault following an incident in Liverpool, while he was also given a suspended four-month sentence for a training ground assault on then City team-mate Ousmane Dabo.
The Dabo incident earned him a six-match ban upon his release from jail, before injury then curtailed his first-team comeback, and his days at the club looked to be numbered as he was sent off in a late-season clash at Liverpool, a game Newcastle lost 3-0 on their way to relegation from the Premier League.
He clashed with manager Alan Shearer in the aftermath and was suspended by the club, but resolved his differences sufficiently enough to remain with them in the Championship under new boss Chris Hughton.
Although injury ruled him out for the middle part of the season he played key roles at the start and end of what was a title-winning campaign.
He went on to become a key figure in the first-team last season, and was understood to be close to extending his stay at St James' Park in January when the bombshell of Andy Carroll's departure for Liverpool dropped.
Talks were put on hold until the end of the season with the player later indicating that he would be happy to stay if captain and friend Kevin Nolan also put pen to paper on a new deal.
But Nolan's exit to West Ham was followed by the news that Barton would be leaving next summer, although recent developments have brought that forward.
Barton's promised tweet arrived 55 minutes later than expected, with him confirming the news and expressing his pride at having worn the club's shirt, while also getting in another dig at the owners.
He said: "Somewhere in those high echelons of NUFC, they have decided, I am persona non grata.
"I am on a free but the honour of wearing those B+W stripes, surpasses that.
"One day the board might realise, what the shirt signifies. HONOUR and PRIDE. Thanks for your continued support........... £toonarmy."