Seven of Formula One's 10 teams have published a joint statement to say they are surprised and shocked by the FIA's confidential agreement with Ferrari over an investigation into the engine it raced with last season.
The teams, which include Mercedes, Red Bull and McLaren, are concerned that the FIA's probe does not identify whether Ferrari bent the rules. They have threatened legal action against the sporting federation.
Aside from Ferrari, Alfa Romeo and Haas - who are all powered by the Italian giants - were the only teams not to put their names to the statement.
Ferrari finished second in the constructors' championship last year, with Charles Leclerc winning twice and Sebastian Vettel once.
The eight teams that finished behind Ferrari in the championship would be rewarded with a hefty increase in prize money if the Scuderia were thrown out.
The statement, which was also signed off by Renault, Racing Point, AlphaTauri and Williams, and comes with the new campaign due to kick off in Melbourne next weekend, read: "We, the undersigned teams, were surprised and shocked by the FIA's statement of Friday 28 February regarding the conclusion of its investigation into the Scuderia Ferrari Formula One Power Unit.
"An international sporting regulator has the responsibility to act with the highest standards of governance, integrity and transparency.
A statement from McLaren Racing. https://t.co/i2UBVwtrCa— McLaren (@McLarenF1) March 4, 2020
"After months of investigations that were undertaken by the FIA only following queries raised by other teams, we strongly object to the FIA reaching a confidential settlement agreement with Ferrari to conclude this matter.
"Therefore, we hereby state publicly our shared commitment to pursue full and proper disclosure in this matter, to ensure that our sport treats all competitors fairly and equally. We do so on behalf of the fans, the participants and the stakeholders of Formula One.
"In addition, we reserve our rights to seek legal redress, within the FIA's due process and before the competent courts."
The PA news agency has contacted both Ferrari and the FIA for their responses to Wednesday's statement.
Suspicions were rife last season that Ferrari exploited a grey area in the rules to increase their fuel flow and boost performance.
The Italian team recorded six consecutive pole positions and amassed three victories before the FIA closed the potential engine loophole ahead of the United States Grand Prix in November.
Ferrari were subsequently off the pace at the Austin race, and the remaining final two rounds of last year in Brazil and Abu Dhabi. They also appeared to be down on power during pre-season testing.
Last Friday, the FIA released a statement saying: "After thorough technical investigations, it has concluded its analysis of the operation of the Scuderia Ferrari Formula One Power Unit and reached a settlement with the team. The specifics of the agreement will remain between the parties."