Mark Catlin has warned it could be years before Pompey are able to pay transfer fees for new recruits.
Matty Blair heads a quartet of new players who could today join the Blues on permanent deals.
All four would be on free transfers – a market Guy Whittingham will have to operate in for a while.
In accordance with Football League stipulations when granting Pompey membership last month, the club are not permitted to buy players.
That is until debts to creditors, primarily the PFA, are settled first.
The Blues owe former players such as Dave Kitson, Liam Lawrence and Tal Ben Haim around £8m in compromise agreements.
As a result, they will be prioritised rather than allowing the club to bring in other players on transfer fees, leaving Whittingham to continue shopping for free agents.
And it is a restriction Pompey’s chief executive agrees with.
Catlin said: ‘This was part of our agreement to get the Football League share (membership).
‘When you look at it, we still owe money to players as part of the compromise agreements and it would be slightly immoral to go and buy players.
‘So, under sanctions put into place by the Football League, we cannot pay money for players until we clear our debts.
‘That is part of the deal and there is nothing we can do about that.
‘Even if we do better than expected financially, part of that will be used to pay debts quicker.
‘It is irrelevant whether the new owners have the funds to start buying players because we are not allowed to do it, anyway.
‘There are authorities owed money such as the PFA and other clubs. But, predominantly, it is the players and their compromise agreements.
‘How long this will be the case is an open-ended question and depends on how well we are going as a club and when debts are paid off.’
Pompey’s remaining two parachute payments from the Premier League will go towards fulfilling those player compromise deals.
The first of them, due in August, will also focus on repaying short-term loans given to the Pompey Supporters’ Trust by property developer Stuart Robinson and Portsmouth City Council.
In the meantime, the Football League have also ruled 50 per cent of any future player sales must be used to reduce debts.
The remainder will be allowed to be used in the running of the football club – but not on transfer fees.
Catlin added: ‘The key is being responsible and that is what being a community club is all about.
‘Some clubs want the rich sugar daddies willing to pump money in to cover players, meaning you are reliant on that person.
‘But as a football club we want to be sustainable and stand on our own two feet.
‘That has to be the way forwards.’