LABOR MP Craig Thomson and union boss Michael Williamson, who is on the ALP national executive, allegedly received secret commissions from a major supplier to their union.

The two men, both senior figures in the Health Services Union at the time, were provided with American Express cards by John Gilleland, who runs a graphic design business, a Sydney Morning Herald investigation has found.

Craig Thomson allegedly received secret commissions from a major supplier to his union. Credit:Andrew Meares

The credit cards were issued in the names of Mr Thomson and Mr Williamson but were attached to Mr Gilleland's account, it was found.

At an HSU function this year Mr Gilleland's wife, Carron, privately complained to senior union officials that Mr Williamson had ''run amok'' with the credit card. According to one official, Mrs Gilleland said, ''he even paid his private school fees on it'' and ''this was not part of the deal''.