A London High Court judge has ruled in favour of Barclays in its bid to significantly reduce a shareholder lawsuit worth up to £560 million ($727 million) over allegations related to its private trading platforms known as dark pools.

Judge Thomas Leech dismissed claims accounting for approximately £330 million of the total value, ruling that investors who only relied on Barclays' share value or listed status could not proceed with their claims.

The case, brought by more than 100 investors including the New York City Teachers' Retirement System and Allianz Global Investors Fund, centres on allegations that Barclays misled clients about its dark pool trading system, Barclays LX, between 2011 and 2016. Dark pools are private stock markets where trades remain anonymous until execution.

The lawsuit followed a 2014 complaint by New York's attorney general that resulted in more than £2 billion being wiped off Barclays' market value. The bank later settled the New York case in 2016, agreeing to pay a $70 million fine and admit to violating securities laws.

During the recent hearing, Barclays' lawyer Helen Davies argued that it was essential for claimants in a shareholder lawsuit to have relied on information published by the listed company, rather than just share value or listed status.

The law firm representing the claimants, Signature Litigation, expressed disagreement with the ruling. "In our view it is not appropriate for Barclays to seek to shut out such investors from the statutory remedy and it is likely we will be seeking to appeal it," the firm said in a statement.

Judge Leech expressed hope that reducing the scope of the claims would improve the chances of reaching an early settlement before the planned trial in October 2025.

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