The suit, which also names BrokerTec parent Icap and technology provider OM, relates to a patent filed by eSpeed in early May. Among other things it demands that BrokerTec cease trading while the suit is pending.

Icap has dismissed the suit as "baseless". In a statement, the firm says: "It seems that eSpeed when faced with real competition has responded by trying to monopolise the US Treasury market using litigation as a means to attack their only electronic competitor."

OM also has denied any wrongdoing. In an effort to reassure customers, the Swedish transaction technology vendor states: "The alleged patent infringement is directed to custom made functionality that is unique to BrokerTec and that does not exist in any other solution that OM has provided to any other customer. The lawsuit is therefore not applicable to, nor can it affect or harm any other OM customer."

ESpeed has experienced considerable success in extracting multi-million dollar pay-outs from US derivatives exchanges for infringements of the notorious Wagner patent, which describes the matching of bids and offers in electronic futures and options trading.

The latest patent, known as the "580" patent, is for "a data processing system for implementing transaction management of auction-based trading for specialised items such as fixed income instruments."

A previous courtroom clash between Icap and Cantor Fitzgerald over staff poaching allegations revealed a deep-seated animosity between the firms. More recently, in a colourful constructive dismissal case, Lee Amaitis, head of Cantor's international operations was forced to deny allegations that he had contemplated using a hitman to take out Icap chief executive Michael Spencer.