Hillary Clinton steps up attacks on Donald Trump

US presidential hopeful Hillary Clinton has attacked her rival Donald Trump's tax history, business acumen and trustworthiness as she sought to capitalise on news that the Republican candidate may not have paid federal taxes for years.

Campaigning at a union hall in Ohio, Democratic candidate Mrs Clinton cast the New York billionaire as a cold-hearted and bungling businessman who "represents the same rigged system that he claims he's going to change".