General Motors has laid out a £40m proposal to develop an internet site that will allow rival carmakers to sell cars alongside those of GM dealers. The site – likely to be called Autocentric.com – will be tested in a US city within six months.

Large dealer groups have shown some resistance but Michael Devereux, director business development, eGM group, said: “Dealers are cautiously optimistic about it.”

General Motors executives, including chief executive officer Richard Wagoner, say the proposed website would help boost flagging sales for GM in the US.