Democrat frontrunner Hillary Clinton has slammed Donald Trump over comments he made prior to the economic downturn in 2008.

The presumptive presidential nominee had said in a 2006 interview, several years before the crash, he hoped the housing bubble would pop "because then people like me would go in and buy".

Clinton's comments come as her campaign released an advert showing the devastation caused by the 2008 crash, stressing that five million people lost their homes, and stating Trump "hoped for it to happen".

"He actually said he was hoping for the crash that caused hard-working families in California and across America to lose their jobs," the Wall Street Journal reported Clinton saying at a campaign event. "All because he thought he could take advantage of it to make some money for himself."

The ad also features audio of Trump saying 'I sort of hope that happens, because then people like me would go in and buy. If there is a bubble burst you could make a lot of money".

Trump has gained support among America's working class, with strong rhetoric on job creation and rebuilding industry resonating with blue-collar workers – many of whom were hit hard by the downturn.

Continuing her attack on social media, Clinton tweeted: "How cruel do you have to be to actually root for a crisis that would devastate millions of families, all to pad your own pockets?" She added: "We need a president who's fighting to raise incomes for all Americans, not one who tries to profit at their expense."

Trump has not yet responded to Clinton's latest attack, which comes just a day after Trump's new campaign video featuring a voice-over of the women who alleged Hillary's husband Bill Clinton had sexually assaulted them.