Andrew Forrest, the billionaire chairman of mining giant Fortescue, has sent a stark warning to staff amid allegations of sexual harassment on the company’s mines.

Andrew "Twiggy" Forrest's mining giant Fortescue has been slapped with a landmark class action alleging systemic sexual harassment, discrimination and toxic work sites.

Fortescue Metals Group has been sued by female workers who allege there is widespread sexual harassment and assault at the company’s remote sites.