The disarray engulfing Newcastle United deepened on Sunday when owner Mike Ashley said he was putting the Premier League club up for sale in response to fans’ hostility against him and the board but had no intention of conducting a fire sale.

The billionaire owner of the Sports Direct retail group issued an impassioned three-page statement defending his stewardship of the club he bought only 16 months ago but acknowledging that the vitriol of Newcastle fans, who held mass demonstrations on Saturday over the departure of manager Kevin Keegan, had got under his skin.

“You don’t need to demonstrate against me again because I have got the message,” he said. Mr Ashley said he had loved taking his children to Newcastle matches and mixing with the club‘s passionate supporters. “But I am now a dad who can’t take his kids to a football game on a Saturday because I am advised I would be assaulted,” he said.

“Therefore, I am no longer prepared to subsidise Newcastle United. I am putting the club up for sale.”

The statement revealed that the owner, who paid £134m for the club, had in all invested £250m, and that the club remained in debt and owes millions of pounds in transfer fees.

He said he was putting the club on “a sound financial footing”, building up a scouting and academy system to find and develop young players. But the problem was that fans wanted immediate success and huge amounts of money to be spent in the transfer market, he said.

“Newcastle does not generate the income of a Manchester United or a Real Madrid,” the statement said. “I am Mike Ashley, not Mike Ashley a multi-billionaire with unlimited resources. Newcastle United and I can’t do what other clubs can. We can’t afford it.”

He said he hoped the fans “get what they want and that the next owner is someone who can lavish the amount of money on the club that the fans want”. But he added: “This will not be a fire sale.”

His decision to issue the statement appears to suggest he has capitulated to fans’ calls for him to sell up. But the possibility of him “flipping” Newcastle has been on the cards ever since he prised the club from the grip of Freddie Shepherd, the long-standing and equally despised former chairman, in May 2007 after buying out Sir John Hall’s majority shareholding.

Rumours of a sale have been around for months, and Anil Ambani, the Indian businessman, publicly ended his interest after failing to get a response from the club. Having invested so much into the club, he will want a price considerably in excess of the £210m Abu Dhabi investors are paying for Manchester City. Mr Ashley is expected to appoint financial advisers in the next few days.

But his heartfelt plea to the fans for understanding also suggests that his Plan B is to try to win them over to his strategy for running the club on “a business and football model that is sustainable”. In the short-term, Mr Ashley has the job of finding someone to fill the post of manager, once one of the most sought-after jobs in English football but now something of a poisoned chalice.

His appointment of Keegan, a folk hero on Tyneside, after sacking former manager Sam Allardyce in January appeared a masterstroke. It endeared him to fans who were sceptical of the intentions of the owner and his coterie of London-based advisers.

But he followed the Keegan appointment by setting up a continental-style management structure which divested responsibility for transfers away from the manager. The move led to Keegan’s resignation 11 days ago over the club’s summer transfer dealings.

On Saturday, fans paraded a banner at Newcastle’s St James’s Park stadium, saying “Cockney mafia out”. Mr Ashley appears to be granting him their wish.