Aston Martin Racing is calling for greater transparency in the GTE Balance of Performance process after its Vantages again proved off the pace in the Austin World Endurance Championship round.
AMR boss John Gaw believes changes to the BoP made ahead of the last month's Nurburgring event have unbalanced the field in GTE Pro and were unnecessary because the balance at the previous six-hour race at Spa in May was "the most equal in the history of the WEC".
He argued that transparent processes need to be put in place so that similar situations are avoided when the new GTE rulebook, which has been conceived to make the BoP process easier, comes into force for 2016.
"When a balanced formula is required at world championship level to control costs, all the manufacturers, the organisers and the suppliers should work better together to ensure what's happened to the competitive situation in WEC GTE post-Le Mans is corrected and not allowed to happen again," Gaw told AUTOSPORT.
"Those who sign off the budgets required for racing in that environment need confidence that as the flag drops to start a race that everyone has a fair chance to win, assuming the execution is at the highest level."
Gaw explained that the manufacturers were working with the FIA and the Automobile Club de l'Ouest, who write the rules, to increase transparency, but insisted that "work will be required now and in the future to ensure key stakeholders that sign off those budgets are convinced that it can deliver".
The Vantage GTEs have raced at each of the past two WEC events with an air-restrictor reduced in diameter by 5mm in comparison with the Silverstone and Spa rounds, which Aston has stated is worth between 10 and 20bhp.
The Ferrari 458 Italia has had its minimum weight raised by 5kg, while the Porsche 911 RSR has been given a 10kg weight break.
There was a separate BoP at the Le Mans 24 Hours because of the unique demands of the 8.47-mile Circuit de la Sarthe.
Porsche finished one-two at both the Nurburgring and Austin, while Aston notched up a best result of fourth each time.
Richie Stanaway and Fernando Rees put their Vantage on pole position at Austin after each used a set of soft compound Michelin tyres, while Ferrari is believed to have qualified on mediums and Porsche used only one set.