Defending champions Red Bull found themselves at the centre of a new technical row on Sunday, just hours before the start of the Monaco Grand Prix.
Rival teams - believed to include McLaren, Ferrari and Mercedes - were said to be unhappy about the design of the floor used by the pole-sitting car to be driven by Australian Mark Webber.
According to paddock sources close to the engineering staff of those teams, they are unhappy at the creation of a 'hole' in the floor of Red Bull's RB8 car, just ahead of the rear wheels.
None of the teams were prepared to make any official complaint about the floor design, but said instead that they hoped it may be discovered and investigated.
Red Bull said it had no comment to make on the issue, but a senior source at the team told Autosport.com that the design had been declared legal by the ruling body, the International Motoring Federation (FIA).
It is believed that the design has been in use on the car since the Bahrain Grand Prix, won by Red Bull's defending double world champion German Sebastian Vettel.
The 'hole' may contravene article 3.12.5 of F1's technical regulations.
It is believed to have been created to improve the airflow under the car and to increase the amount of rear end down-force, which in turn would improve the car's handling.
Webber took pole position for the team on Saturday after clocking the second-fastest time behind seven-time champion German Michael Schumacher of Mercedes who was given a five-place penalty for crashing during the Spanish Grand Prix two weeks earlier.