Kirk Kerkorian, the billionaire US investor, is walking away from a year-long boardroom tussle with General Motors by selling a quarter of his stake in the US car manufacturer.

Kerkorian started building his stake in the company in May 2005 and by September last year held 56 million shares, a 9.9% stake. He paid between $31 and $26.17 per share according to filings with the US Securities and Exchange Commission.