The PFA have warned EFL clubs that a proposed salary cap will be "unenforceable and unlawful" ahead of a vote for League One and League Two clubs on Friday.
League One and Two clubs will vote today over imposing £2.5m-a-year and £1.5m-a-year limits on player wages.
EFL chairman Rick Parry is keen to push it through an agreement to guard against irresponsible spending in the future after the financial impact brought on by the coronavirus pandemic.
Bury, Bolton Wanderers and Macclesfield Town are just three clubs in the lower-league to have suffered serious financial problems this season, whilst Championship outfit Wigan Athletic were relegated after a 12 points deduction for entering administration.
However, on the eve of the vote, the PFA have warned that any agreement would be "unlawful".
A statement read: "Ahead of the EFL vote tomorrow, the PFA has sent a report to all club Chief Executives and the EFL regarding the proposed salary caps for League One and Two.
"The report has raised concerns that the proposed cap is being rushed through, without proper consideration or consultation.
"Like everyone involved in football, we want to see sustainable clubs at all levels. We absolutely understand and appreciate the huge economic pressure that clubs have come under due to the COVID-19 crisis.
"However, we have significant reservations about the measures being proposed and the speed at which these are being implemented.
"The introduction of a salary cap in English football represents a seismic change. It is a change that will have far-reaching and significant impacts right across the professional game. We must take the time to ensure that these are properly considered and understood.
"We have been surprised and disappointed at the level of consultation and engagement around these proposals so far.
"It is, undoubtedly, in the best interests of the clubs, the leagues and the players that we work together on this important issue.
"Today, we have invited the EFL to a period of expedited arbitration in August, before the next season starts and the transfer window closes, in order to reach a shared agreement on the way forward.
"The EFL has a legal obligation to consult with the PFA and the Professional Football Negotiating and Consultative Committee (PFNCC), over any potential changes to a player’s conditions.
"This consultation has not happened, and as such, we are gravely concerned that any cap brought in will be unlawful and unenforceable, which will ultimately be detrimental to everyone involved."
