After a week, Treasury Secretary Steve Mnuchin - rather than Rettig - told Neal that the returns weren't yet available, as "t$3 he committee's request raises serious issues concerning the constitutional scope of Congressional investigative authority, the legitimacy of the asserted legislative objective, and the constitutional rights of American citizens".
"I am aware that concerns have been raised regarding my request and the authority of the Committee".More news: GM to reveal next-generation Corvette in July
"Even if Ways and Means had a legitimate committee goal for requesting the President's tax returns and return information, that objective is not driving Chairman Neal's request", he wrote.
Mr Trump himself has claimed that he can not release his tax returns because they are under audit, although technically there is nothing preventing him from doing so.
Trump broke with 40 years of presidential campaign tradition by declining to release his personal returns before the 2016 election. Experts have repeatedly pointed out that being under audit does not preclude the release of such information.
"The legal implications of this request could affect protections for all Americans against politically-motivated disclosures of personal tax information, regardless of which party is in power", Mnuchin wrote.More news: Man arrested after boy falls from balcony at Minnesota's Mall of America
Mnuchin said that Treasury Department lawyers have been working "diligently" to research the issues involved and have been in contact with Justice Department attorneys. With an eye to a legal challenge, Neal told Rettig that he has two weeks to respond - by 5 p.m. on April 23. "Please know that if you fail to comply, your failure will be interpreted as a denial of my request".
The president has long maintained he will not release his returns while under audit. Neal also could seek the returns through a subpoena.
A lawyer for Trump said in a letter last week that the efforts are an attempt to harass a political opponent and that it would set a "dangerous precedent" for the agency to turn them over.
At congressional hearings, Mnuchin accused lawmakers of seeking Trump's returns for political reasons.More news: Steph Curry goes down with ankle injury in 1st quarter against Pelicans
Donald Trump will have to release five years of tax returns if he wants appear on the IL 2020 presidential ballot, the state's senate has ruled.