A House of Commons public spending watchdog has accused BBC chief Mark Thompson of illegally supporting Microsoft. In failing to ensure iPlayer on demand services are available to all licence fee payers he has been blinded by the novelty of the internet, it's charged.

As part of a Public Accounts Committee session on BBC procurement last Tuesday, the director-general was grilled by Liberal Democrat John Pugh MP on the decision to release the download version of the iPlayer for Windows and Internet Explorer only. The move has prompted anger from Mac, Linux and Firefox users.

Thompson claimed the Christmas day marketing launch of the service had been a great success. "All the feedback we've had is that consumers are enormously enjoying using iPlayer. About a million people in this country have tried it already."

Pugh followed up the meeting with a letter to Thompson on Wednesday. He wrote: "By guaranteeing full functionality to the products of one software vendor [the BBC] is as a public body handing a commercial advantage to that company - effectively illegal state aid!

"What might be a pragmatic choice for a privately funded company becomes deeply problematic for a public corporation."

Pugh is the MP for Southport and takes particular interest in IT issues, especially around public sector procurement and interoperability.

The Open Source Consortium, a lobby group for Linux, has vowed to pursue its illegal state aid complaints in European Court if the BBC does not release the iPlayer application for other operating systems and browsers soon.

Thompson erred under Pugh's questioning over the current level of interoperability offered by the iPlayer desktop application. He was asked: "At what stange will you be able to download and stream to a Mac or a Linux computer?"

"You can do that now," Thompson replied.

He later recanted the statement, conceding that only streams are currently available on non-Windows computers. "We will get those [downloads] as soon as possible," he said, noting the two-year deadline set by the BBC Trust.

"I recognise and welcome the assurances that the BBC and you personally have given on this subject but wonder whether the sheer novelty of the new media has blinded many to the clear commercial inequity in the delivery of it," Pugh replied in his letter. He argued that the plan to release Mac and Linux versions within two years is not "sufficient excuse for past sins or indeed much of an explanation".

In previous public statements, the BBC has insisted that desktop versions for Mac and Linux were not developed because it could not provide the Digital Rights Management demanded by TV production companies.

In a statement on Friday, the BBC said it will respond to Pugh's letter in due course. "We would like to underline our commitment to universal access to BBC iPlayer, as with all other BBC services, which BBC director-general Mark Thompson reiterated to the Public Accounts Committee on Tuesday," it added.

Video of the session is available here (relevant passage begins at 12 minutes 15 seconds). We've published the full text of Pugh's letter on the following page. ®