Barclays has confirmed it is facing a £720 million lawsuit by deal-maker Amanda Staveley over emergency fundraising during the financial crisis.
Ms Staveley told the Financial Times that a lawsuit for damages had been filed with the High Court, but did not make any further comments.
In 2008, her company, PCP Capital Partners, invested £3.5 billion on behalf of Abu Dhabi's Sheikh Mansour bin Zayed Al Nahyan, with Barclays securing a further £5.3bn from Qatari investors.
Barclays sought emergency funding to strengthen its capital position and reduce the possibility of needing a government bailout.
In 2013, the Financial Conduct Authority (FCA) said Barclays "acted recklessly", and did not properly disclose certain parts of the deal with Qatar. The regulator accused the bank of secretly making payments to Qatari investors worth £322m in return for the £5bn investment. But Barclays said the payments were for advice given.
The Serious Fraud Office is conducting a criminal investigation into the matter.