Dealmaker Staveley, who played a prominent role in Abu Dhabi's Sheikh Mansour bin Zayad al Nahayan's investment in Barclays at that time, is suing the bank at the High Court in London.

"We believe the claim against Barclays is misconceived and without merit and Barclays will be vigorously defending it," the bank said in a statement.

A spokesman for Staveley's PCP Capital Partners confirmed the claim had been filed but did not give any details.

The Financial Times earlier reported the lawsuit would seek nearly 1 billion pounds ($1.4 billion) from Barclays in the dispute.

Barclays avoided a state bailout during the financial crisis by securing almost 12 billion pounds from two emergency cash injections, mostly from Middle Eastern investors.

British and U.S. authorities have for several years been investigating commercial agreements made between Barclays and Qatari investors as part of the capital raising.

($1 = 0.6972 pounds)

(Reporting by Jane Merriman; Editing by Rachel Armstrong and Mark Potter)