Relegated Charlton are considering legal action following the news Sheffield Wednesday's 12-point deduction for breaching financial rules will be imposed next season.
The Addicks, who finished 22nd in the Sky Bet Championship, would have stayed up at the expense of Wednesday had the sanction been applied to the 2019-20 campaign.
An independent disciplinary commission, appointed under English Football League regulations, punished the Owls after deeming they should not have included profits from the sale of Hillsborough stadium in statements for the period ending July 2018.
The South Yorkshire club said it was "extremely disappointed" with the verdict but welcomed the decision not to enforce the penalty this term.
Charlton, who are set to drop into League One alongside Wigan and Hull, are less enamoured with the timing of the sanction, branding it "irrational".
"The club is considering a legal challenge following the news that Sheffield Wednesday will receive a sporting sanction that will take effect in the 2020-21 season," read a Charlton statement.
"We fail to understand why the deduction will take place next season rather than the current season, which seems to be irrational, and are writing to the EFL to get an explanation of the justification."
Wednesday finished 16th in the Championship, eight points clear of the drop zone.
Had their penalty been applied to the 2019-20 season, they would have plummeted to the bottom of the division, sparing Charlton.
Lee Bowyer's Addicks only finished in 22nd position because Wigan, who accumulated three more points than Garry Monk's Owls over the course of the campaign, were deducted 12 points for entering administration.
Unlike Wednesday's situation, which relates to financial accounts from 2018, EFL rules dictate a club entering administration is punished immediately, something the Latics' ownership were aware of when that decision was made.
The demise of Wigan, who are awaiting the outcome of their appeal, resulted in Barnsley staying up on the final day of a campaign prolonged by the coronavirus pandemic.
While Charlton intend to contact the EFL about the matter, the timeline of Wednesday's appeal and punishment was determined by the independent disciplinary commission.
The Owls, owned by Thai businessman Dejphon Chansiri, intend to await written reasons for the sanction and "consider the full detail with its legal advisers" before deciding its next step.
They were cleared of a second charge of acting in bad faith by "deliberately concealing information" from the EFL.
"Sheffield Wednesday acknowledges the decision of the independent disciplinary commission announced today," read a club statement.
"The club is extremely disappointed that the commission has imposed a 12-point deduction to be applied next season and awaits the written reasons for this decision.
"The club welcomes the decision that the commission cleared Sheffield Wednesday of the charge of acting in bad faith in its dealings with the EFL. Further, the commission decided not to apply a 12-point deduction this season, thereby imposing relegation."
Hillsborough was sold to a company owned by Chansiri for around £60million.
The EFL charge, brought in November 2019, related to "how and when" the stadium deal was completed.
Without the transaction, Wednesday would have posted a pre-tax loss of £35.4million for the financial year covering the 2017-18 campaign.
The EFL statement read: "An independent disciplinary commission, appointed under EFL regulations, has ruled that Sheffield Wednesday will receive a 12-point deduction for breaching the league's profitability and sustainability rules for the three season reporting period ending with season 2017-18," read an EFL statement.
"The sporting sanction will take effect in season 2020-21."
