EU antitrust regulators fined Microsoft 561 million euros on Wednesday for breaking a promise to offerEuropean consumers a choice of web browsers.

Microsoft's regulatory troubles in Europe date from the last decade and has already cost it a total 2.16 billion euros, including the latest fine.

The fines relate to an anti-trust battle in Europe more than a decade ago. In order to avoid a penalty then, Microsoft promised to offer European consumers a choice of rival browsers.

EU anti-trust regulators said this did not happen for a period during February 2011 and July 2012, a lapse Microsoft blamed on a technical error. It has said it since tightened internal procedures to avoid a repeat.

The latest lapse did not escape the notice of Microsoft's board, which cut the bonus of chief executive Steve Ballmer last year, partly because of the Windows division's failure to provide a browser choice screen as required by the European Commission, according to an annual proxy filing.

Microsoft's share of the European browser market has roughly halved since 2008 to 24 percent in January, below the 35 percent held by Google's Chrome and Mozilla's 29 percent share, according to Web traffic analysis company StatCounter.

Presented by Adam Justice