The Portsmouth Supporters Trust is confident that the Football League will enforce a 10-point deduction on the club this season, claiming Pompey have suffered enough during their spectacular slide down the divisions.

Portsmouth were relegated to League Two on Tuesday night following Oldham Athletic's victory over Yeovil Town and will return to the fourth tier for the first time since 1980, but the Guardian understands that the Football League will punish them this season, rather than next.

Pompey were given special dispensation last August to begin the campaign on zero points despite confirmation they would be deducted 10 due to an unsatisfactory first company voluntary arrangement. It had been mooted that the Football League would deem a deduction on an already relegated club to be no punishment at all, but it intends to implement the sanction during the current campaign once Portsmouth exit administration, which they expect to do this week.

"We feel that although the punishment hasn't technically been activated yet, its effects have certainly been felt from day one of this season," said PST's Colin Farmery. "We feel that we've served the punishment and that it has had an effect on our season, so the points ought to come off now.

"We knew that they were going to come off – although we started the season on zero points, mentally everyone started on -10 points. If you are told that you will lose 10 points at some point during the season, you never budget for those points. If you look at it like that then we have been punished.

"If we were to end up with a 10-point deduction next season it would feel like we are being punished twice for the same offence. We certainly feel that as a football club we can look in the eyes of a supporter from any other club and say we have been punished for the sins of others considerably over the last three years. We were in the Premier League and FA Cup final – we've suffered three relegations and had 29 points taken off us."

Ashley Brown, the PST chairman, had previously said it would be "devastating" if the 10-point sanction was imposed next season, with Portsmouth's future now finally appearing stable despite a second successive relegation.

Pompey were playing in the Premier League three years ago and won the FA Cup in 2008, but have slid down the divisions due to catastrophic financial mismanagement by a number of owners. However, following an 11th-hour deal struck at the high court last week regarding the valuation of Fratton Park, PST will become 51% shareholders under a new structure.

Once they exit administration Portsmouth are expected to appoint a new chief executive and confirm that the caretaker manager, Guy Whittingham, will take up the post on a full-time basis.

Farmery added: "The really big challenge is about to begin and that's a really exciting. Everyone's been resigned to League Two football since January and the fact that we knew we were going to lose 10 points as well really put the tin lid on it. As a club we've played at this level in the past and while we feel we should be playing in a higher division because of our status, we're in the division we deserve to be in.

"Once we come out of administration we can start functioning as a normal football club again. We've got a number of players on loans or short-term contracts and the ones that our new management team want to keep we should be able to provide the resources for.

"We've been a pretty sick club for three or four years now but we've ended this season well and there is confidence that we can take into next year. We have a medium-to-long-term plan to get back into the Championship."