Donald Trump and his businesses sued the Democratic chairman of the House Oversight committee on Monday to block a subpoena requesting the president's financial records.
In a court filing in Washington, the president's lawyers argued congressman Elijah Cummings "has no legislative purpose" to issue the subpoena and accused Democrats of using their majority in Congress to harass him.
“The Democratic Party, with its newfound control of the US House of Representatives, has declared all-out political war against President Donald J Trump," the lawsuit stated. “Subpoenas are their weapon of choice.”
The lawsuit asked the court to block a subpoena issued to Mr Trump’s accounting firm, Mazars, last week demanding several years of the president's financial statements.
The lawsuit, which will be fiercely contested in court, follows a string of moves in recent weeks by Mr Trump and his businesses to block the Democrats from getting their hands on his financial records.
It came after Michael Cohen, Mr Trump's longtime former lawyer, told Congress that Mr Trump had inflated his company's assets to obtain a loan in a failed attempt to buy the Buffalo Bills football team.
Cohen, who has pleaded guilty to several crimes including tax fraud and lying to Congress in 2017, submitted portions of documents called "statements of financial condition" to the House Oversight committee ahead of his testimony in February.
Cohen's testimony led Democrats in Congress to demand the release of Mr Trump's statements of financial condition and his tax returns for the last six years - something he has refused to do voluntarily, bucking the trend of recent presidential candidates.
In his lawsuit on Monday, Mr Trump called Cohen's testimony "a partisan stunt, not a good-faith effort to obtain accurate testimony from a reliable witness".
In a statement, Mr Trump's lawyer, Jay Sekulow, said: "We will not allow presidential harassment to go unanswered."
A spokeswoman for Mazars said the company would “respect this process and will comply with all legal obligations”.
Mr Cummings has previously said his committee has the "full authority" to investigate whether the president engaged in illegal conduct before and during his time in office and whether he had any undisclosed conflicts of interest.
He gave Mazars, which prepared financial statements for loan applications for Mr Trump, an April 29 deadline when he issued the subpoena.
Responding to Mr Trump's lawsuit yesterday he said there was no “valid legal basis to interfere with this duly authorised subpoena from Congress”.