The European Commission has halted its investigation into the purchase by Microsoft and Time Warner of ContentGuard, the group that develops anti-piracy technology for the media and entertainment industry.

The move comes after Thomson, the French technology group, said it would join the two US groups and take a 33 per cent stake in ContentGuard.

Thomson's participation has eased some of Brussels's competition concerns about the merger, which had been the subject of formal allegations by the Commission last month. The Commission had been due to rule on the merger by January 6th. That deadline will now be extended.