Renault have accused McLaren of driving "a cart horse through the spirit" of Formula One with their new rear wing even though it has been approved by the sport's ruling body.

"It is fundamentally clear that the McLaren wing design is totally illegal," Bob Bell, Renault's managing director Bob Bell told the BBC after the first practice session of the season at the Bahrain grand prix today.

"They have driven a cart horse through the spirit of the rules and regulations," said Bell. "They have opened up another arms race, it's going to cost everybody a lot of money. The governing bodies need to be a lot stronger with these things."

Renault themselves are competing under a suspended permanent ban after the race-fixing controversy that cast a shadow over last season.

The McLaren car passed inspections yesterday at the Sakhir circuit and the team maintained that they consulted the FIA, Formula One's governing body, throughout the design process.

Patrick Head, the Williams co-owner and engineering director, told Reuters that the rear wing had a slot that appeared to be fed by a duct that the McLaren drivers Jenson Button and Lewis Hamilton could block at will by body movement.

"I understand that [race director] Charlie [Whiting] is saying that article three of the regulations that would limit something like that don't apply to the driver, only to the car," he said. "But I do remember when our active ride car was banned, it was banned on the grounds that a piston in the strut was moving and by virtue of doing so was influencing the aerodynamic performance of the car. "What I'm told Charlie is saying is that Lewis or Jenson's knee, or whatever it is, is not part of the car.

"It is a bit of a problem because if one car is suddenly able to gain five or six km an hour on the straight then we've all got to do it," he added.

He speculated that drivers might conceivably drive one-handed down the straight with the other hand covering the flow of air through a hole in the cockpit to secure an aerodynamic advantage.

The Red Bull team manager Christian Horner said: "The FIA have looked at it and deemed it to be okay. It's therefore a clever design rather than an illegal design. The question is, is the driver part of the car? They deem him not to be.

"Inevitably now there will be a wild goose chase of all the teams chasing that loophole. We have to come up with another solution. Anything's possible."

Asked if there would be a protest, Horner added: "I don't know. We're happy with the verdict from the FIA. We wanted clarity and we have that."