Claire Jeffs

Joined firm 1998. Partner since 2005.

Claire is Co-Chair of the Competition Group globally and works in Slaughter and May’s Brussels and London offices.

Claire has extensive experience of both EU and UK competition law. She has been involved in a large number of high-profile merger cases before the EU and UK competition authorities, as well as coordinating merger approvals worldwide. On the contentious side, she has been involved in many cartel and other behavioural cases, including on appeal to the General Court in Luxembourg.

Highlights include advising:

  • Suez on the public takeover bid by Veolia
  • Facebook on its proposed acquisition of Kustomer
  • Vodafone on its acquisition of parts of Liberty Global
  • Shire on its takeover by Takeda
  • Google in relation to the European Commission’s antitrust investigation into its AdSense for Search advertising services and its appeal of the decision to the General Court.

Claire has been named in W@Competition’s list of ‘40 in their 40s Notable Women Competition Professionals’ and The Lawyer’s Hot 100 list. She was awarded ‘Dealmaker of the Year’ by Global Competition Review in 2017 and 2022, and shortlisted in the ‘Lawyer of the Year’ category in the 2019 Global Competition Review awards.

Claire is listed as a ‘Leading Individual’ by Chambers and The Legal 500, and recognised as a ‘Thought Leader’ in Who’s Who Legal: Competition. 

She is a member of the Brussels Bar (A list), as well as being qualified as a solicitor (England and Wales).

Claire is fluent in French and Russian and has good German.

Recent publications include: