WASHINGTON - Whistleblowers claiming the Justice Department improperly interfered with a years-long investigation into Hunter Biden will testify before Congress today as House Republicans accelerate their probes into the president and his family.

Leaders of the House Judiciary, Oversight and Accountability, and Ways and Means committees will lead a hearing with two Internal Revenue Service employees - Greg Shapley and an as-yet-unnamed “whistleblower x” - who claim there was a pattern of “slow-walking investigative steps” into Hunter Biden, including delayed enforcement actions in the months before the 2020 election won by Joe Biden.

It will be the first public testimony from the two IRS agents assigned to the federal case into President Joe Biden’s youngest son, Hunter, which was focused on tax and gun charges. The second agent, whose name was withheld in interview transcripts released by Republicans, is expected to have his identity revealed at the hearing.

The congressional inquiry into the Justice Department’s case against Hunter Biden was launched last month, days after it was announced that the younger Biden will plead guilty to the misdemeanor tax offenses as part of an agreement with federal prosecutors.

The House Ways and Means Committee voted to publicly disclose hundreds of pages of testimony from the IRS employees in which they described several roadblocks agents on the case faced when trying to interview individuals relevant to the case or issue search warrants.

One of Shapley’s most explosive claims was that U.S. Attorney David Weiss in Delaware, the federal prosecutor who led the investigation, asked to be provided special counsel status in order to bring the tax cases against Hunter Biden in jurisdictions outside Delaware, including Washington, D.C., and California, but was denied.

Both Weiss and the Justice Department have vehemently denied such claims, saying that he had “full authority” of the case and never sought to bring charges in other states.

The second IRS whistleblower described his persistent frustrations with the way the case was handled, dating back to the Trump administration under Attorney General William Barr. He said he started the investigation into Hunter Biden in 2015 and began to delve deeply into his life and finances. Republicans have also sought testimony from other agents involved in the case but have been mostly unsuccessful thus far.

Republicans, including the three chairmen - Reps. Jim Jordan of Ohio, James Comer of Kentucky and Jason Smith of Missouri - have sought to paint the Justice Department’s case as rife with political interference and bias.

They have also called the plea agreement Hunter Biden made with prosecutors to likely avoid jail time a “sweetheart deal.”

Ahead of the hearing, Comer acknowledged it has been difficult for Republicans to succinctly outline Hunter Biden’s tangled financial affairs or to provide convincing evidence of any specific wrongdoing by the president or his family.

“It’s so hard to explain,” Comer told reporters at the Capitol.

“Hopefully these IRS agents can do a better job explaining than I can,” he said.

High-ranking officials at the Justice Department have countered these claims by pointing to the extraordinary set of circumstances surrounding a criminal case into a subject who at the time was the son of a leading presidential candidate.

And it remains unclear how much of the conflict the whistleblowers describe amounts to internal disagreement about how to pursue the wide-ranging probe or a pattern of interference and preferential treatment. Department policy has long warned prosecutors to take care in charging cases with potential political overtones around the time of an election, to avoid any possible influence on the outcome.