A Brisbane night-fill worker has won an important legal battle in a massive underpayment case against the combined might of Coles and one of the largest trade unions in Australia.

Coles worker Penny Vickers, who was representing herself, won the right for a full bench hearing in the Fair Work Commission against the arguments of high-powered lawyers from the company and the Shop, Distributive & Allied Employees (SDA).

Coles supermarket employee Penny Vickers has won the right for a full bench hearing in the Fair Work Commission. Credit:Glenn Hunt

Her case is the latest attempt to unwind controversial deals struck by the politically influential SDA with major companies which have left workers out of pocket.

A 12-month Fairfax Media investigation revealed how deals involving big business and the conservative SDA left more than 250,000 workers paid less than the award - the wages safety net - and is estimated to have saved those employers at least $300 million a year.