Australia's biggest car dealership group has become the latest company to confess to underpaying its staff, revealing that 6200 employees were deprived of $4.5 million in pay over seven years.

AP Eagers said it had brought PwC in for an external review in July after identifying ''anomalies'' in its payroll systems, which had resulted in a total shortfall of $4.5 million. It affected about half of the group's workforce, who will be repaid in full and with extra interest based on a formula of the Reserve Bank of Australia's cash rate each year plus 4 per cent.