Australia's largest horticulture company Costa Group – a major supplier to Coles and Woolworths – has been accused of undercutting the wages and conditions of its low paid workers.

Costa's berry business – marketed under the brand Driscoll's – has been forced to withdraw a workplace agreement after it was challenged by a union for being much worse than the award, the basic wages safety net.

Former Geelong Football Club president Frank Costa remains a large shareholder in the Costa Group. Credit:Josh Robenstone

Costa Group started trading on the stock market on Friday and is the family company of prominent businessman and ex-Geelong Football Club President, Frank Costa, who remains a large shareholder.

It is expected to have revenue in excess of $700 million this financial year.