The London Stock Exchange is being sued for unfair dismissal by Eli Lederman, formerly the chief executive of Turquoise.

Lederman led Turquoise – a dark pool or anonymous trading venue founded by seven investment banks – until the company was bought by the LSE in February 2010. He was replaced by David Lester, who had been group chief information officer.

In case that begins on Thursday at a London employment tribunal, Lederman claims the LSE acted in an “unacceptable and unreasonable” manner in the lead up to his departure, according to various reports.

The LSE declined to comment. Lederman said the restrictions during his “gardening leave” were also unfair.

Lederman said he took the decision to sue "when it became clear that other members of the Turquoise team were also pursuing claims against the LSE". It is not clear if other claims have been filed.

“Serious questions still remain about the LSE Group’s compliance with its legal obligations to disclose relevant evidence in its possession,” he said in an email yesterday, reported by Bloomberg. “To date, no e-mails related to my dismissal have been disclosed from Xavier Rolet or between LSE Group and any bank shareholder.”

In other news, after the LSE bought Turquoise the exchange made a number of system changes at the dark pool venue. With Lester at the helm, it ripped out the existing Cinnober TradExpress platform and introduced the Millennium Exchange system from Sri Lankan supplier Millennium IT, which it had recently acquired.

Since trading on the new system began, the LSE has had several lengthy, high profile outages. The exact reasons have not been disclosed, but this month Computerworld UK revealed that changes to closing auction procedures had caused severe market data system troubles.