Some of Europe’s top law firms face being probed by Financial Services Authority (FSA) as part of an investigation by the regulator into some of the year’s biggest M&A deals.

The FSA is reviewing four major transactions completed in the past 12 months where information is thought to have been leaked. The body is questioning everyone involved in the deals and has already held more than 50 detailed discussions with organisations such as law firms, banks, PR companies, printers and issuers.