The European Union's patience with Microsoft is fast wearing thin after the software titan accused it of collusion with its rivals.

EU competition commissioner Neelie Kroes has warned the company it faces fines of up to €2 million ($2.4m; £1.3m) a day, backdated to mid-December, unless it obeys a 2004 antitrust order to provide competitors with the information needed to make their software work with Microsoft servers.

The Seattle-headquartered giant has accused the Commission of "inappropriate contacts" with competitors and of violating its rights of defence, following a report in February by British computer scientist Neil Barrett that the data Microsoft has so far provided is unworkable.

The company, which originally approved Barrett's appointment as an independent monitor, is now questioning the impartiality of his advice.

Microsoft's appeal against the original 2004 antitrust ruling and the consequent €497.2m ($597.2m; £340.5m) fine is to be held in Luxembourg next month.

Data sourced from Financial Times Online; additional content by WARC staff