Ford has reversed a decision to hand all of its advertising business to WPP, following an internal inquiry which found the directive from British-born company president Sir Nick Scheele breached internal guidelines.

There is no suggestion that the car maker, which is the British advertising group's largest single customer and accounts for 7% of revenue, will remove its business. It may even push more business to WPP. Ford has been hit by dire conditions in the automotive market. It is looking to cut costs across all divisions and has consolidated many contracts with single suppliers.

Sir Nick's WPP directive was in line with that policy but appeared to have been issued in a way that went against internal procedures. The inquiry also raised concerns because Sir Nick is a friend of WPP boss Sir Martin Sorrell and his son works for one of the advertising firm's subsidiaries.

WPP handles about 80% of Ford's advertising accounts, including its Ford, Lincoln, Mercury, Jaguar and Land Rover brands.

Analysts expect any further business awards to WPP to be made at low rates, reflecting the large sums already paid by the car company.

The inquiry has sparked fears of boardroom infighting at Ford. It was launched by David Thursfield, Ford's global purchasing chief and the executive most often seen as a successor to the 59-year-old Sir Nick.