Currently managed by Guy Whittingham, the south coast club has been in financial ruin for some time and have been in administration twice since February 2010.
Stuck in the League One drop zone, the 2008 FA Cup winners have had to release six players from their temporary contracts in the transfer window, and lost leading goalscorer Izale McLeod, who returned to Milton Keynes Dons.
Clarke has admitted time is of the essence if the Pompey Trust Supporters Group want to take control at Fratton Park.
He said: “Portsmouth are at the last chance saloon. They can’t enter another season in administration. So they either sort themselves out before the start of next season or they are out of the Football League.”
Having to rely on short-term contracts for free agents and temporary loan deals, the club did complete the signing of former Charlton defender Sam Sodje on Thursday, and hope to extend the contract of veteran defender Ricardo Rocha.
Pompey play Hartlepool at Fratton Park on Saturday.
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