WASHINGTON (Reuters) - Treasury Secretary Steven Mnuchin on Thursday declined a request by the Democratic chairman of the U.S. House of Representatives tax committee to testify next week about the partial government shutdown’s impact on the upcoming federal tax filing season.

FILE PHOTO: U.S. Treasury Secretary Steven Mnuchin speaks during his interview with Reuters in Jerusalem October 21, 2018. REUTERS/Ronen Zvulun/File Photo

In a letter to House Ways and Means Committee Chairman Richard Neal, the Treasury Department offered to send senior officials “who are most knowledgeable” about the department’s plans during the shutdown.

The Internal Revenue Service said this week it would bring more than 46,000 furloughed employees back to work to handle tax filings, refunds and other tasks.

Democrats have been mulling the possibility of hearings since the White House said earlier this month that the IRS, the federal government tax agency that Treasury oversees, would deliver tax returns during the shutdown.

“If the purpose of the upcoming hearing is to inform Congress and the public, we are confident that goal will be best served by testimony from the senior department officials with the deepest and broadest expertise on the subject of the hearing,” Jennifer Bang, Treasury deputy assistant secretary, said in the letter to Neal, which was released by the panel.

Neal responded sharply to Mnuchin’s refusal to appear.

“With more than 70,000 Treasury employees furloughed and missing paychecks, I strongly believe Secretary Mnuchin himself should appear before our committee and answer members’ questions,” Neal said in a statement after Mnuchin declined the invitation to appear on Jan. 24.

About one-quarter of the federal government shut down on Dec. 22 over President Donald Trump’s demand for $5.7 billion to fund a wall along the U.S.-Mexico border, which Democrats oppose. The shutdown entered its 27th day on Thursday, with no end in sight for nearly 800,000 federal employees who are no longer being paid.

Meanwhile, the U.S. tax filing season is set to begin on Jan. 28 and last until the April 15 filing deadline.

On Wednesday, the IRS said it would give some taxpayers a break by waiving penalties for many who had too little federal income tax withheld from their pay last year, or who paid less than their estimated tax liabilities.

After a sweeping Republican overhaul of the U.S. tax system, the IRS released updated federal tax withholding tables last year to reflect adjustments in the tax law. But tax authorities later acknowledged that the tables did not fully factor in some changes including exemptions for dependents and reduced itemized deductions.

Democrats, who criticized the withholding tables as inaccurate, are now raising questions whether the IRS can provide refunds on time.