Ford and its teams have been lobbying for changes to the Mustang's aero package for the Great Race this weekend amid fears the Chevrolet Camaro package is too strong.
However, the changes would have fallen outside an official parity review, creating an awkward situation where support from the Chevrolet teams was required.
Unsurprisingly there was strong opposition from the GM armada which has led to the proposed changes being rejected.
That decision hasn't gone down well with the Blue Oval teams, which joined forces in a statement expressing the collective disappointment in both the decision and the overall disparity.
The statement also rules out any form of boycott this weekend, following speculation that the Fords would sit out today's opening practice session as a protest.
"Following ongoing analysis, Supercars, in conjunction with its independent CFD partner, D2H Group, have acknowledged that there continues to be a disparity between the Gen3 Ford Mustang and Chevrolet Camaro," the statement read.
"Therefore, technical parity has still not been achieved. Unfortunately, the proposed aerodynamic changes to the Ford Mustang, which have been acknowledged by all parties involved to reduce the delta between the two models, will not be implemented for the Bathurst 1000 this weekend.
"The independent data shows that the Mustang will be at a continued disadvantage for the biggest race of the year, which we believe is unacceptable – and not what our sport is built upon.
"While disappointed in the situation, every Ford team will be doing their utmost this weekend, it's what the fans deserve, it's what our partners deserve, it's what the Great Race deserves.
"We will continue working together to correct the imbalance going forward, but now, our attention turns on track, respecting the challenge that the Mountain provides."
A further statement from the Ford Motor Company expressed 'deep disappointment' at the outcome while claiming the General Motors entries have a "clear advantage" as a result.
"Ford has long been requesting data transparency to assist in understanding the disparity that exists between the two cars. Unfortunately, this has been rejected on multiple occasions," read the manufacturer's statement.
"The latest parity review was initiated when Supercars computational fluid dynamics (CFD) partner D2H Group provided aerodynamic data of both cars to the homologation teams on August 24. This data clearly demonstrated that aerodynamic parity had not been achieved.
"Since that time, Ford and DJR have engaged with Supercars in good faith to create an aerodynamic update package that would bring the Ford Mustang and the Chevrolet Camaro Gen3 Supercars closer to aerodynamic parity.
"Unfortunately, on the eve of the Bathurst 1000, the Supercars Board has refused to allow the changes which would bring the Ford Mustang and the Chevrolet Camaro closer to technical parity."
The all-important parity system requires the threshold to be met in either five consecutive races or five of the last eight races byt thanks to Ford's stronger showing at The Bend SuperSprint, which made up three of the last four races, the threshold hasn't been met.
Explaining its decision, Supercars said: "Throughout the year, our teams have followed, and Supercars has administered, a Parity Review System for the Repco Supercars Championship," read a statement from Supercars.
"This system serves as the process for evaluating and implementing parity adjustments under the rules and regulations for the category.
"The Parity Review System has a trigger point of a potential parity imbalance being demonstrated in five consecutive races or five out of eight consecutive races.
"The prescribed number of parity triggers showcasing a parity imbalance, as outlined in the system, have not been met at this time and there is no scope for a parity adjustment to be made for the Bathurst 1000 under the Parity Review System.
"Supercars received a request from the Ford homologation team to implement a parity adjustment in advance of the Repco Bathurst 1000 outside of the Parity Review System.
"Supercars considered the request in accordance with the terms of the Teams Racing Charter and the Supercars rules and regulations, which require the consent from all Supercars teams to implement the requested parity adjustment change.
"After numerous meetings with all teams and key stakeholders, the requisite consent from the Supercars teams has not been established to support the requested parity adjustment for the 2023 Repco Bathurst 1000.
"We value the input and perspectives of all involved parties and aim to continue working in a manner that preserves the integrity of our sport and the rules and regulations that govern it."
