Image caption The two firms will pay more than half a billion US dollars in antitrust fines

Japan's Yazaki Corporation and Denso Corporation have agreed to plead guilty and pay fines for fixing prices of parts supplied to US manufacturers.

Yazaki will pay $470m (£300m), the second-largest antitrust fine in US history, while Denso has agreed to pay $78m.

The two auto part makers have been accused of fixing prices for as long as ten years.

Four Yazaki executives will also serve up to two years in a US prison.

"Our investigation is still active and ongoing," said Sharis Pozen of the Department of Justice's Antitrust Division.

'Pernicious cartel'

Yazaki and Denso are among the world's largest auto part suppliers. Any conspiracy to fix prices of parts by such major players is likely to have an impact on the overall cost of manufacturing the vehicles and also affect the selling price.

In order to prevent any recurrence, the company has intensified its various efforts including conducting thorough internal investigations Yazaki Corporation

The Justice department's Ms Pozen said the consumers were financially hurt and authorities were working to ensure that such instances do not happen in the future.

"Criminal antitrust enforcement remains a top priority and the Antitrust Division will continue to work with the FBI and our law enforcement counterparts to root out this kind of pernicious cartel conduct," she said.

The Justice department did not give details of which US manufacturers were affected and how much extra they had to pay.

Yazaki said that it was fully cooperating with the US authorities and had also launched an internal probe into the matter.

"In order to prevent any recurrence, the company has intensified its various efforts including conducting thorough internal investigations, reviewing internal rules, conducting regular educational programs and monitoring activities," the firm said in a statement.