In a statement the law firm has filed 'requests for re-examination' regarding two patents held by TT and says the requests "cite substantial new questions of patentability regarding the claims of each patent".

TT has sued around sixteen futures brokers over the last two years over its patented MD Trader technology - an order-entry screen that displays multiple prices so that users can judge the depth of a market - which is part of its X_Trader order entry platform.

But James Katz, a partner at the law firm, claims that the order entry system TT patented in 2000 is similar to one adopted several years ago by the Tokyo Stock Exchange (TSE).

Katz says this example was not provided to the patent office during the initial examination process.

"We are confident that this evaluation will result in the patents being narrowed or even found to be invalid," he adds.

TT has said that the law firm is recycling a claim from its currrent litigation against Cantor Fitzgerald subsidiary eSpeed, but the Chicago vendor says if the patent office decides to grant the re-examination request it is confident that the validity of its patents will be upheld.

Although it has secured settlements and loyalty agreements with a number of ISVs and broker-dealers over its patented technology, TT is still contesting suits against GL Trade, CQG and RCG while its litigation against eSpeed is set to resume on 28 June at the US District Court for the Northern District of Illinois.