Toyota driver Ralf Schumacher has criticised Ferrari for refusing to restrict their in-season testing.
Ralf Schumacher is unhappy with Ferrari's testing advantage
All nine other Formula One teams agreed to test on just 30 days this year to cut spiralling costs.
Schumacher said: "We restrict ourselves and Ferrari carry on testing happily. I don't understand this. What they are doing is unfair to everyone else.
"We're interested in F1 carrying on for a long time, while Ferrari are not. That's not the right way."
Ferrari chose not to sign up to the gentleman's agreement for two reasons.
They have concentrated their resources on testing, with two private test tracks and a full test team.
And they say they are at a disadvantage because they are the only top team on Bridgstone tyres, while rivals Michelin have data from Renault, McLaren, BAR, Toyota and Williams to work from.
The Italian giants felt the benefits of their massive testing programme at the weekend, when Ferrari's Michael Schumacher bounced back from a poor start to the season to finish second in the San Marino Grand Prix.
Asked whether the testing deal is beginning to collapse, Toyota boss John Howett said: "I think it already has.
"I don't think the other competitors can just sit there and accept Ferrari driving into the distance.
"We need to find some sort of compromise where there is either an equivalence or Ferrari join the remaining teams otherwise people will start to test remorselessly.
"I think they will force others to do that. I think it is a question of common sense."
BAR-Honda team chief Nick Fry added: "Frankly I'm glad (Fernando) Alonso won because if Ferrari had won it would have been a hollow victory and I would have felt very sorry for Renault.
"It would have been fairly un-sportsmanlike in some ways had Ferrari revelled in a victory when we have handicapped ourselves deliberately by [limiting testing] to keep costs down.
"Ferrari are flaunting that and this is the result.
"BAR have done more testing than any other team, but Ferrari have done 85% more miles than we have by totally ignoring the gentleman's agreement between the teams and putting themselves in a better position.
"Ferrari undoubtedly will start winning. You cannot test in the way they test with their resources and not benefit versus the rest of us. It was inevitable they would come back."