Acting White House chief of staff Mick Mulvaney said on Fox News Sunday that Democrats will "never" see President Trump's tax returns.

"Nor should they. That’s an issue that was already litigated during the election. Voters knew the president could have given his tax returns. They knew that he didn’t and they elected him anyway," said Mulvaney, adding that Democrats "know they're not going to" get the tax returns."

"They just want attention on the issue because they don’t want to talk to us about policy."

MIck Mulvaney says that the democrats will never see President Trump's taxes and that they know they won't #FNS pic.twitter.com/DDjFmjGz8f — FoxNewsSunday (@FoxNewsSunday) April 7, 2019

On Wednesday evening, Ways and Means Committee Chairman Richard Neal (D-MA) said that he had filed a formal request with the Treasury, asking IRS Commissioner Charles Rettig to turn over six years' worth of the president's tax returns, putting Rettig's boss - Treasury Secretary Steven Mnuchin, in the hot seat.

On Friday, President Trump said that the law is "100 percent" on his side over his decision not to release his returns while he's under IRS audit.

"Hey, I’m under audit. But that’s up to whoever it is. From what I understand the law is 100 percent on my side."

President Trump: "From what I understand, the law is 100% on my side" in battle with Democrats over release of tax returns. https://t.co/eaFJf8g2ry pic.twitter.com/2fbEvRLQqT — The Hill (@thehill) April 5, 2019

Speaking of Democrats who have "no interest in working with this President," Mulvaney also told Fox News that the Democrat party is "infested" with what we call "Trump Derangement Syndrome," adding "they still can't accept that he won the election."

Mick Mulvaney tells @billhemmer that the democrats will never stop investigating the President #FNS pic.twitter.com/EAaYLf1PAL — FoxNewsSunday (@FoxNewsSunday) April 7, 2019

Mueller report

Mulvaney said that Democrats were "caught flat footed" by the Mueller report's conclusion of no collusion with Russia. "They really did believe that Mueller would find collusion and find obstruction, in fact they had invested very heavily in that."

Mick Mulvaney tells @billhemmer that the democrats really didn't see the Mueller report concluding with no collusion #FNS pic.twitter.com/YnIC0xdJYW — FoxNewsSunday (@FoxNewsSunday) April 7, 2019

Border crisis

When asked what the plan was to get out of the current border crisis, Mulvaney said that Mexico has to do more to prevent immigrants from entering Mexico, and that they need to accept people that the United States sends back over the border. The acting CoS also said that Congress "must act," adding that "the laws are what's acting as this giant magnet for these illegal immigrants, and Congress has to change those laws."

Mick Mulvaney tells @billhemmer there are 3 things that really need to happen to end the border crisis pic.twitter.com/PkGxBh6Csp — FoxNewsSunday (@FoxNewsSunday) April 7, 2019