House Ways and Means Committee Chairman Richard Neal issued a subpoena to Treasury Secretary Steve Mnuchin and Internal Revenue Service (IRS) Commissioner Charles Rettig for six years of President Trump's personal and business tax returns.

Mnuchin has refused to provide the tax returns to Neal, who first requested them on April 6, claiming that Congress does not have a legitimate purpose to see them. Neal has argued that Congress' oversight responsibilities allow the committee to see how the president has complied with tax laws.

Mnuchin rejected Neal's request in a letter earlier this week, after Neal had given him the deadline of Monday to comply.

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"In reliance on the advice of the Department of Justice, I have determined that the committee's request lacks a legitimate legislative purpose, and pursuant to section 6103, the department is therefore not authorized to disclose the requested returns and return information," Mnuchin wrote.

Now, Neal is citing a statute that gives the chairman of the House Ways and Means Committee the authority to obtain any individual's tax return as justification for obtaining Mr. Trump's tax returns. Mr. Trump's personal attorney had suggested in a letter to Mnuchin in April that the Department of Justice should decide whether Mr. Trump's tax returns could be disclosed to Neal.

The administration is not likely to comply with Neal's subpoena. White House Chief of Staff Mick Mulvaney told CBS News this week that Congress would never see Mr. Trump's tax returns, saying that Congress is "not entitled to see them by law."

However, Congress may still be able to get access to Mr. Trump's state tax returns. The New York state Senate passed a bill on Wednesday which would require the release of any state tax returns requested by the chair of the federal House Ways and Means Committee, the Senate Finance Committee, or the Joint Committee on Taxation.

The bill is likely to pass the state Assembly, which is also controlled by Democrats, and to be signed by Democratic Gov. Andrew Cuomo, a frequent critic of Mr. Trump.

Rebecca Kaplan contributed to this report.