Kevin Keegan has resigned as manager of Newcastle United after just eight months and 21 games in charge.

The announcement follows lengthy talks between the 57-year-old and the board.

"I've been working desperately hard to find a way forward with the directors, but sadly that has not proved possible," Keegan said in a statement released on Thursday evening via the LMA.

"It's my opinion that a manager must have the right to manage and that clubs should not impose upon any manager any player that he does not want."

He added: "It remains my fervent wish to see Newcastle United do well in the future and I feel incredibly sorry for the players, staff and most importantly the supporters.

"I have been left with no choice other than to leave."

Mike Ashley was understood to have to have flown to Tyneside for talks with Keegan on Thursday afternoon to try and resolve the situation.

Keegan is the second Premier League manager to resign in as many days following the departure of Alan Curbishley from West Ham on Wednesday.

Newcastle have employed seven managers since Keegan's first spell ended in 1997.

Kenny Dalglish, Ruud Gullit, Sir Bobby Robson, Graeme Souness, Glenn Roeder and Sam Allardyce all came and went before Keegan's return.

After Keegan missed training on Wednesday - with reports suggesting he was in Manchester discussing his situation with a legal team - the club released a short statement saying that he has not been sacked and that talks between the Board and Keegan were ongoing.

Reports on Wednesday also suggested that Keegan was in talks with his lawyer's over his position, with Sky Sports News claiming that Keegan would owe the club £2million if he quit his post.

On Tuesday, Newcastle released a statement after several hours of speculation that he had been sacked which led to an angry protest from over 1,000 fans outside St James' Park.

The statement read: "Kevin has raised a number of issues and those have been discussed with him.

"The Club wants to keep progressing with its long-term strategy and would like to stress that Kevin is extremely important, both now and in the future.

"Newcastle United values the effort and commitment shown by Kevin since his return to St. James' Park and wants him to continue to play an instrumental role as manager of the Club.

"For the avoidance of doubt the Club has not sacked Kevin Keegan as manager."

The news that Keegan could be on his way out of the club first came after it was reported earlier on Tuesday that Keegan was holding a hastily arranged meeting with Mike Ashley.

Keegan was unhappy about future plans and failed transfer deals, with reports that Dennis Wise had pulled the plug on a proposed deal for Lazio defender Gugliemo Stendardo and that Ashley had stated that every player in the squad was for sale if the price was right.

Keegan was appointed Newcastle manager for a second time in January after the sacking of Sam Allardyce.

It was reported shortly after his arrival that he was unhappy with restructuring at the club which saw Dennis Wise appointed as executive director.

Newcastle's only business on transfer deadline day was a £5.7million swoop for Spanish striker Xisco and the loan signing of midfielder Ignacio Gonzalez from Valencia.

OddsPreview.com undertands that both deals were conducted by Wise and fellow director Tony Jimenez, with Keegan unaware of either player.

Wise and Jimenez were also heavily involved in the signings of Fabricio Coloccini and Jonas Gutierrez, although Keegan was involved in the signing of Danny Guthrie.

Keegan was also unhappy that the club had sold James Milner to Aston Villa last week in a £12million deal. Keegan, a huge fan of the winger, had just days before the transfer said there was no chance of the player being sold.

Keegan's loyalty to Joey Barton, who the club tried to offload on Monday, has also caused problems behind the scenes.