A Hollywood director has accused Microsoft of deliberately stoking a format war between Blu-ray and HD-DVD.

Michael Bay, who directed Transformers, Armageddon and Bad Boys, alleged that Microsoft had deliberately tried to cause confusion over the next media format so that it could sell downloads.

Bay was asked by a fan on his web forum why his films were so slow to be released on Blu-ray, which the fan favoured. Bay blamed Microsoft for his use of the HD-DVD format.

"What you don't understand is corporate politics. Microsoft wants both formats to fail so they can be heroes and make the world move to digital downloads," he said.

Bay alleged that Microsoft is "handing out $100m cheques to studios just to embrace HD-DVD and not the leading, and superior, Blu-ray".

"They want confusion in the market until they perfect the digital downloads. Time will tell and you will see the truth," he said.

Bay's complaints echo those who claim that Paramount dropped its Blu-ray titles after receiving a payout of marketing funds.