Formula One can sustain 12 separate and competitive teams only if some are allowed to enter cars designed and made by others, FIA president Max Mosley said on Monday.

"There are all sorts of commercial discussions going on but, to me, it's self evident that Formula One hasn't got enough money for 12 different teams to have 12 research and development programmes, 12 wind tunnels, 12 organisations getting on for 1,000 employees (each)," he told Reuters on Monday.

"That means you either have 'customer cars' or you have people struggling at the back of the grid being lapped four times in the race," he added, speaking after the launch in London of the first U.N. Global Road Safety Week.

"To me it's obvious you should have the customer cars. Whether you have four cars of a given make or two on the grid, it doesn't seem to matter. They will all look completely different anyway."

Formula One's current rules stipulate that teams must design and build their own cars but the governing International Automobile Federation has said that will no longer be the case in 2008, when Prodrive are due to become the 12th team.

Prodrive boss David Richards plans to enter cars with the chassis and engine provided by one of the sport's leading manufacturers.

The issue has overshadowed the start of the season, with tail-enders Spyker taking rivals Super Aguri and Toro Rosso to arbitration for allegedly entering cars that are in breach of the rules.

Spyker say the Super Aguri is a version of last year's race-winning Honda while the Toro Rosso has been designed by Red Bull's Adrian Newey.

Super Aguri and Toro Rosso say they have acted within the rules.

Spyker team boss Colin Kolles said at the last race in Bahrain that Formula One supremo Bernie Ecclestone was drawing up a proposal to try to resolve the dispute.

He hoped Ecclestone would establish that there was a difference between a constructor and an entrant, defining what benefits each could expect.

Mosley said that, in his opinion, there should not be a distinction between the two.

"In the end in 2008, it won't be a problem," he said. "In 2007, there is a dispute about what the Concorde Agreement means and it is right and proper that if there is a dispute it should go to arbitration."

The Concorde Agreement is a confidential document that governs the commercial side of the sport