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 Sunday's friendly defeat at Leeds, before saying he would make an announcement on his future at 4pm on Monday. 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 www.nufc.co.uk read: "Newcastle United can 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 on Sundat 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''.