Derek Llambias, Newcastle's managing director, has resigned from his position with immediate effect.
The shock announcement follows yesterday's appointment of Joe Kinnear as the club's director of football.
Kinnear had said in his talkSPORT interview on Monday night that Llambias had already resigned and that he would concentrate solely on the finance side of the club. That allegation was emphatically denied by the club, but this morning Llambias told the owner Mike Ashley that he would be leaving.
Llambias had been Ashley's right hand man inside St James' Park before the controversial of introduction of Kinnear.
"I have had an incredible journey during my five years at the club, including some challenging times," said Llambias. "I will reflect with great fondness on my time in the North East and, in me, Newcastle United have a lifelong supporter.
"I want to thank the staff for their hard work, our fans for their support of the club, and wish them all well for the future."
Llambias, who used to be in charge of the exclusive Fifty Club casino in London, moved to St James' Park in 2008 to take over the day to day running of the club.
He was influential in introducing a new business model at the club, one which refused to buy ageing players with no add on fees and along with Ashley, Llambias set about trimming the wage bill that the new owner had inherited when he bought the club. More emphasis was put on self sufficiency.
There were controversies; the renaming of St James' Park, the Wonga deal and the sacking of Chris Hughton less than six months after promotion from the Championship as champions.
There were also key sales under Llambias with Kevin Nolan, Joey Barton and Andy Carroll all departing during his watch. Finishing fifth in the 2011-2012 season was cited as justification for the controversial methods put into place by Ashley and Llambias.
But last season was a struggle, despite a run to the quarter-final of the Europa League ,and the appointment of Kinnear has created a new bout of controversy.
His departure leaves a gap in the financial operation of the club, an area Kinnear has so far expressed no desire to take over.