White House press secretary Sarah Sanders on Sunday slammed members of Congress as not 'smart enough' to read the 10 years of tax returns Democratic lawmakers have requested from President Donald Trump.

'I don't think Congress - particularly not this group of congressmen and women - are smart enough to look through the thousands of pages I would assume that President Trump's taxes will be. My guest is most of them don't do their own taxes. And I certainly don't trust them to look through the decades of success that the president has and determine anything,' she said on 'Fox News Sunday.'

She was also clear the president would not hand over his tax reforms.

'The president has been clear from the beginning - as long as his tax are under audit he's not going to release them,' she said.

White House press secretary Sarah Sanders slammed members of Congress as not 'smart enough' to read President Trump's tax returns

And she attacked the section of law Democrats used to request the president's returns, which is a provision that allows Congress to request tax forms to see how changes to the tax code could affect people's returns.

'This has nothing to do with whether or not they are going to determine policy. This is all about political partisanship. This is a dangerous, dangerous, road,' she said.

Rep. Richard Neal, the House Ways and Means Committee chairman, gave the IRS until April 23 to hand over President Trump's returns, telling the tax agency that the law clearly gives Congress a right to them.

The government's failure to respond by the deadline could send the dispute into federal court.

Neal's demand on Saturday came after the Trump administration asked for more time to consider his initial request last week.

Neal, a Massachusetts Democrat, argues that a 1920-era law saying the IRS 'shall furnish' any tax return requested by Congress 'is unambiguous and raises no complicated legal issues' and that the Treasury Department's objections lack merit.

Rep. Richard Neal, the House Ways and Means Committee chairman, has given the IRS until April 23 to hand over President Donald Trump's tax returns

Trump has said that he will not release his tax returns because he is under audit

The letter to IRS Commissioner Charles Rettig is the latest exchange in a tug of war over Trump's returns, which would give lawmakers far greater insight into the president's business dealings and potential conflicts of interest as it exercises its oversight role.

Trump declined to provide his tax information as a candidate in 2016 and as president, something party nominees have traditionally done in the name of the transparency.

During the campaign, Trump said he wanted to release his returns but said because he was under a routine audit, 'I can't.'

Being under audit is no legal bar to anyone releasing his or her returns. And after the November midterm elections, Trump claimed at a news conference that the filings were too complex for people to understand.

IRS Commissioner Charles Rettig will have until April 23 to meet the new demand

Rep. Richard Neal, the House Ways and Means Committee chairman, wrote the letter

Asked repeatedly at a House hearing Tuesday whether any regulation prohibited a taxpayer from disclosing returns when under audit, Rettig responded 'no.'

The issue appears sure to end up in federal court. With an eye to a legal challenge, Neal told Rettig that he has two weeks to respond - by 5pm on April 23.

If Rettig fails to do so, Neal said he will interpret as denying the request, which could pave the way for a court battle. Neal also seeks the returns through a subpoena.

Treasury Secretary Steven Mnuchin, who oversees the IRS, told Neal this past week that he needs more time to consider the unprecedented demand for Trump's returns and needs to consult with the Justice Department about it.

Mnuchin accused lawmakers of seeking Trump's returns for political reasons. But he also acknowledged his 'statutory responsibilities' and that he respects congressional oversight.

Some Treasury-watchers observe that Mnuchin's decision to consult with the Justice Department could suggest that Treasury lawyers believe Neal has a legal right to Trump's returns.

Neal said Saturday that the administration has no right 'to question or second guess' his motivations.