The European Commission could be dragged into a series of legal battles with bondholders in Spain's Banco Popular in the next fortnight in what would be a key test of Europe's first major bank resolution.

Lawyers for firms that lost €850m of bonds in Popular are preparing to file a claim for damages against the Commission and its Single Resolution Board by August 17 — the last possible date to bring an action under European limitation rules — according to people familiar with the situation. Any claim would be filed at the European Court of Justice.