NSW Police have executed search warrants at the upmarket Westin Hotel in Sydney and a union related credit union and seized documents in relation to investigations into rorting allegations about former Labor MP Craig Thomson.

Along with the documents, the Sydney-based fraud squad detectives are believed to have taken hotel CCTV screen shots dating back to 2005.

Union records show that Mr Thomson stayed at the Westin in Sydney's CBD in May 2005, paying a total of $255.53.

A statement issued by the NSW Police Fraud and Cybercrime Squad's Strike Force Carnarvon on Tuesday said: "Investigators also served a notice to produce at a state government employees credit union in Clarence Street, Sydney."

Mr Thomson's lawyer, Chris McArdle told News Ltd: "It's a pity they are wasting their time. They should be chasing real criminals."

The now independent federal MP is charged with 154 counts of fraud, allegedly committed while he was national secretary of the Health Services Union.

Mr Thomson has denied all allegations of wrongdoing.