MG Rover is blaming a reduction in the volume of parts bought and the need to buy some items from BMW for a price increase.
In a letter to parts managers, MG said: "Parts purchase volumes have reduced significantly in recent years and suppliers, particularly those with ongoing current parts supply contracts, are taking the opportunity to review unit prices. This has resulted in requests for significant price increases and/or minimum order quantity constraints."
The document adds that BMW's continued ownership of the Longbridge powertrain and Swindon body pressings operations had resulted in "significant increases in cost prices".
MG Rover puts these increases at an average of 10%, but says it will be absorbing the majority of the costs.