Bill Theobald

USA TODAY

Hillary Clinton continued to turn up the heat Saturday on Donald Trump 's refusal to release his tax returns.

Her campaign released a video online Saturday titled "What's Donald Trump Hiding?" that includes a series of clips over the years of Trump being asked whether he plans to release his returns.

Trump says he won't release his returns until an audit of his taxes is complete.

In an interview Friday with ABC News' George Stephanopoulus, Trump replied "it's none of your business," when asked what his tax rate is.

Trump: My tax rate is 'none of your business'

The Clinton video, which runs about one minute, ends asking "what is Donald hiding?" It follows comments the Democratic frontrunner made to supporters earlier this week, when she said: “So you’ve got to ask yourself, why doesn’t he want to release them? ... Yeah, well, we’re going to find out.”

Fact check: Trump’s tax returns

Clinton has not yet released her 2015 tax returns, but years worth of her and former President Bill Clinton's tax information is available on her website.

Meanwhile, former GOP presidential candidate Mitt Romney said this week that Trump's refusal to release his tax returns is “disqualifying” for the presidency.

Romney: Trump's refusal to release tax returns 'disqualifying'

In a Facebook post Wednesday, Romney said the returns provide the public with information about the candidate's charitable giving, wealth and other dealings.