Vladimir Antonov has resigned as chairman of Portsmouth after the club's parent company was placed into administration just a week after he was granted bail following the collapse of a bank he owned.
The Russian businessman, whose company Convers Sports Initiatives bought Pompey in June, has also quit as a director of the club.
However, the company responsible for operating the actual team -- Portsmouth Football Club Limited -- is still trading and is not in administration, though it is now seeking fresh funds.
"After the extraordinary amount of work put in by so many people over the last 18 months to get to this point, it is incredibly disappointing for the club to find itself in this position," said Portsmouth chief executive David Lampitt.
"I want to assure staff and fans that we will continue to do everything possible to safeguard the position of the club and its longer-term future."
A Portsmouth statement said: "The club's parent company, Convers Sports Initiatives plc (CSI), has been placed into administration. Vladimir Antonov has resigned as chairman and director of Portsmouth Football Club.
"The club has funding in place for the short term, but will now be seeking alternative investment for its longer-term requirements."
Last week Antonov was granted conditional bail by an English court as Lithuania tried to extradite him over the collapse of the bank he owns.
Antonov is wanted as part of a probe at Bankas Snoras, Lithuania's fourth-biggest bank, which went into state administration earlier this month.
He has been accused of involvement in misappropriating 897 million litas ($344 million, 260 million euros) and forging documents to cover it up.
Portsmouth, who in 2008 won the FA Cup, were relegated from the Premier League at the end of the 2009/10 season -- when they again reached the FA Cup final -- after being deducted points for entering administration.
At the time the south coast club had debts of £130 million ($203 million) and were on the verge of liquidation when Hong Kong-based businessman Balram Chainrai took over in October.
Despite starting last season with a threadbare squad, Portsmouth did, under the guidance of manager Steve Cotterill, manage to stay in the second-tier Championship, rather than drop yet further into the third division.
But earlier this term Cotterill left to join divisional rivals Nottingham Forest and Portsmouth are currently, with 20 points from 18 matches, just above the relegation zone.
Were the club to enter administration again, they would likely be hit with another points deduction -- a huge blow to their hopes of remaining in the Championship.