After one of the most calamitous collapses ever witnessed in football, the fate of Portsmouth's battered husk has fallen to be determined between two quite opposed forms of ownership thrown up by the modern game. In one corner is the Pompey Supporters Trust, lifelong fans, united around the concept of mutual and democratic ownership of the club, whose crumpling has been felt as a trauma to something they hold dear. In the other corner is Balram Chainrai, the Hong Kong-based businessman who had no previous connection to Portsmouth, who lent money to the club at substantial rates of interest and does not want to lose it.

Trevor Birch, the former footballer turned insolvency accountant whose firm, PKF, was appointed to handle this – Portsmouth's second administration in two years – has given the trust and Chainrai two weeks, until 5pm next Friday, to finalise their bids for the club. Both are expected to do so, although Chainrai withdrew his bid last month, complaining about Birch's fees and failure to find anybody else willing to take Pompey over, and "the negative criticism and lack of support for our takeover by fans".

Chainrai lent around £18.6m to Portsmouth in 2009 while, still a Premier League club and the FA Cup winners in 2008, they teetered on the brink of their first fall into insolvency. Chainrai has never seen that money again but has always since held a grip on the club's ownership. Unlike others owed many millions in the long, sorry list of Portsmouth's creditors, Chainrai had secured his loans with a mortgage over Fratton Park and the club itself. These mortgages were held by his company, Portpin, registered in the tax haven of the British Virgin Islands.

Those mortgages meant that when Portsmouth fell into administration in February 2010, while a battalion of local businesses, HM Revenue and Customs, St John Ambulance and others lost all their money, Chainrai took possession of the club with his £18.6m still secured and owed to him in full.

The club and all its assets were transferred to a new company, owned by Chainrai, with a commitment to pay creditors 20p for every pound they were owed – £16.5m for the £83m outstanding from the collapsed club. Then came the next dismal chapter: Chainrai sold the club in June last year to a Russian banker, Vladimir Antonov, who took on the new company's commitments and began to spend money on players and their wages. Six months later Antonov was arrested in London on a European warrant for alleged massive bank fraud issued by the prosecutor general of Lithuania, a charge Antonov is contesting.

Antonov's company, Convers Sports Initiatives, rapidly went into administration as, in February, did Portsmouth, again. Of the £16.5m committed to the creditors from the club's first administration, not a penny had been paid and it all sits as just a claim on this new company's administration with which Birch is wrestling.

Chainrai, via Portpin, still had a mortgage registered on Fratton Park to secure his £18.6m, so he has always held a controlling position in what can happen to the club now. Although he has consistently said he does not want to own a football club, he says he saved Portsmouth by taking them out of administration last time. This time, in a brief conversation with the Guardian, Chainrai said from Hong Kong that he is no longer personally involved, that he is leaving the negotiations to Portpin but he does not want to lose too much of the money he loaned to the club.

His proposal to take the club back again will involve him paying in a relatively small amount to settle the £40m of creditors this time round, and for him, via Portpin, to retain his mortgage over Fratton Park. The proposal would lead to the creditors of the first Portsmouth administration receiving less than a penny in the pound, rather than the 20p pledged, and not having voted to approve that, because the liquidator of the old Portsmouth company did so on their behalf. The Football League has said it is unhappy with that and, if those original creditors do not get the opportunity to vote themselves, then Portsmouth – their depleted team already in League One's relegation places – will be deducted 10 points.

The league has also insisted that Chainrai must cut the £18.6m debt he has secured against Fratton Park, if Portsmouth are to be accepted back into the league. That has opened up the opportunity for the supporters trust, which believes it can mount a convincing bid.

The trust is working with a property developer, Stuart Robinson, who is expected to offer for Fratton Park a price assessed at its market value, around £2.6m. Ashley Brown, the chair of the trust, says it has amassed sufficient money from its 2,000 members and some wealthy individual supporters to offer Birch around £850,000 to settle the club's debts. The creditors would still lose almost all their money but Brown says the trust would be determined never to allow the club to fall back into the wretched position to which it has sunk since 2009. Then, Alexandre "Sacha" Gaydamak, the owner who supported Harry Redknapp's spending on an all-star, Cup-winning team with more than £30m of loans, said he could not continue, and the club plummeted, from the Premier League to peril.

Now, on one side, stand the supporters, organised into a trust, according to the progressive thinking English football has developed while so many of its great clubs have been bought by businessmen from overseas. A fans' takeover of Portsmouth will be a major landmark for supporter ownership in the game.

On the other side is Chainrai, a businessman, determined not to lose too much of the money he lent to the club in a previous crisis. In the middle is Birch, who must decide which offer is ultimately better for Portsmouth's creditors, who will have to write off all but a fraction of their money, whichever side wins.