Joe Kinnear resigned as Newcastle's director of football on Monday night after a turbulent week on Tyneside.
The former Magpies manager stepped down from his post just days after the club sold star midfielder Yohan Cabaye and failed to replace him before Friday's transfer deadline.
A club statement said: "Newcastle United can confirm that Joe Kinnear has this evening resigned from his position as Director of Football with immediate effect.
"The club will be making no further comment."
Kinnear, who was appointed on a three-year contract in June last year, leaves St James' Park having not made a single permanent signing during his tenure with only strikers Loic Remy and Luuk de Jong having joined Newcastle on loan.
The 67-year-old was a controversial appointment last summer as owner Mike Ashley responded to a desperately disappointing season which saw the club finish in 16th place in the Barclays Premier League despite an investment in excess of £30million in new players during the January transfer window.
Manager Alan Pardew, who had guided them into fifth 12 months earlier, kept his job after an end-of-season review, but only just with Ashley deeply unhappy with what he had witnessed.
His response, to general disbelief, was to ask Kinnear to head up the football side of the business.
The former Wimbledon manager's appointment went down like a lead balloon with fans who remembered his first spell on Tyneside, when an ill-fated five-month reign as Kevin Keegan's replacement was eventually ended by illness before Alan Shearer was recruited in a vain attempt to prevent the club being relegated.
It was equally unpopular with managing director Derek Llambias, who resigned to end his association with Ashley at St James'.
Kinnear, who had launched his managerial career on Tyneside with a four-letter rant at journalists, pre-empted his return in a series of increasingly bizarre interviews in which he trumpeted his suitability for the job.
Kinnear then urged fans to judge him on his signings, and the chorus of disapproval reached a deafening volume last week.
Having not made a single permanent signing during the summer transfer window, Kinnear oversaw the sale of Cabaye - a player he had at one point referred to as "Yohan Kebab" - to Paris St-Germain.
But with Pardew, who had not wanted to lose the Frenchman, insisting the club had to replace their playmaker if they were to stand any chance of maintaining or improving upon their current standing of eighth, they were unable to push home their interest in either Lyon's Clement Grenier or Montpellier's Remy Cabella.
Hours after the transfer window closed, Newcastle were trounced 3-0 by arch-rivals Sunderland on their own pitch for the second successive season and Shearer believes a combination of all those factors could well have led to the former Wimbledon manager's resignation.
"The life at Newcastle United," he told BBC Radio 5 Live.
"I shouldn't say I'm surprised but I was surprised in the first place when he was announced director, particularly the way the news was broken when Joe himself announced it on the radio when he got some of the players' names wrong.
"What has he been there now, about seven months? And two players have come in, albeit both players on loan.
"Maybe it's Newcastle's way of trying to say that the performance on Saturday wasn't good enough and why they didn't get any new players in, maybe that's one of the reasons.
"But they can only get players in if there's one man prepared to sign a chequebook."
He added: "You just never know what goes on at Newcastle behind closed doors.
"I think we were all surprised because Joe had been out of football for so long. Let's say that we hope he's okay and it's nothing to do with ill-health but it's just bizarre sometimes at Newcastle.
"Four, five weeks ago Newcastle were going so well, still in the FA Cup, Alan Pardew was getting manager of the month awards (and) they were looking up the league rather than finishing in mid-table.
"It's amazing what happens in three or four weeks in football, 3-0 on Saturday hurt everyone and they were second best all over the park on Saturday with a lack of fight and a lack of desire from the players and now it's come to this."