Seven Formula One teams have joined forces to oppose the FIA's decision to reach a private settlement with Ferrari over an investigation into their 2019 engine.
Last week, motorsport's governing body said an agreement was reached with the Scuderia over a long-running analysis into the outfit's power unit amid questions raised by the car's impressive straight-line speed.
Ferrari always denied any wrongdoing but a collection of rival teams released a joint statement to voice a "strong objection".
Mercedes, Red Bull, McLaren, Renault, Racing Point, Alpha Tauri and Williams co-signed the letter. Haas and Alfa Romeo – who both use Ferrari engines – did not sign.
The teams say they are exploring the next steps, which could involve legal action to ensure "full and proper disclosure" from the FIA.
"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 1 Power Unit," the statement read.
"An international sporting regulator has the responsibility to act with the highest standards of governance, integrity and transparency.
"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."