WASHINGTON — The Democratic chairman of the Senate Judiciary Committee vowed Thursday to take “seriously” an IRS whistleblower’s claim of a cover-up in the long-running criminal investigation of first son Hunter Biden.

“We take all whistleblower statements seriously, as we should. Some turn out to be very important and some not,” Sen. Dick Durbin (D-Ill.) said during a hearing on judicial nominees. “But we take them all seriously at the outset and look at them closely.”

Durbin was responding to the top Republican on the panel, Sen. Lindsey Graham (R-SC), who called for a “bipartisan” embrace of the currently unidentified IRS employee — who on Wednesday informed key congressional committee leaders that he has information on “preferential treatment” and false testimony to Congress about the case.

“I hope the committee will take this seriously,” Graham said Thursday morning.

“I think [Senate] Finance and [House] Ways and Means have the first shot at this. But the whole idea that maybe the investigation was compromised was a DOJ matter, not just an IRS matter, and many of us worked in a bipartisan fashion with the Mueller investigation,” Graham added.

“And I don’t know where this leads, but I do know we need to embrace the idea that we’re gonna look long and hard at any accusation that investigation was compromised. And I hope we can do that in a bipartisan fashion.”

The White House has declined to comment on the potentially explosive development in the criminal and congressional inquiries into the first family’s overseas business dealings.

“We’ve been very clear to not comment on anything related to any type of investigation,” White House press secretary Karine Jean-Pierre told CNN Thursday morning.

“Since he took office and consistent with his campaign promise that he would restore the independence of the Justice Department when it comes to decision-making in criminal investigations, President Biden has made clear that this matter would be handled independently by the Justice Department, under the leadership of a US attorney appointed by former President [Donald] Trump, free from any political interference by the White House,” administration spokesman Ian Sams told The Post in an email Thursday. “He has upheld that commitment.”

A lawyer for the whistleblower informed Congress on Wednesday afternoon that he wants to expose “preferential treatment” in the criminal investigation and false testimony to Congress by a “senior political appointee.”

“My client has already made legally protected disclosures internally at the IRS, through counsel to the US Treasury Inspector General for Tax Administration, and to the Department of Justice, Office of Inspector General,” attorney Mark Lytle wrote.

“The protected disclosures: (1) contradict sworn testimony to Congress by a senior political appointee, (2) involve failure to mitigate clear conflicts of interest in the ultimate disposition of the case, and (3) detail examples of preferential treatment and politics improperly infecting decisions and protocols that would normally be followed by career law enforcement professionals in similar circumstances if the subject were not politically connected.”

A quirk of federal law requires congressional permission for the whistleblower to consult with their attorneys on the substance of tax issues, which the whistleblower is seeking from Senate Finance Committee Chairman Ron Wyden (D-Ore.) or House Ways and Means Committee Chairman Jason Smith (R-Mo.).

Lytle addressed his Wednesday letter to the top Republican and Democratic members on the Senate Finance and Judiciary committees and on the House Judiciary and Ways and Means committees, in addition to whistleblower caucus co-chair Sen. Chuck Grassley (R-Iowa).

Hunter, 53, isn’t named in the letter, but congressional sources confirmed the complaint pertains to the first son, who reportedly borrowed about $2 million last year to pay off a tax bill assessed on income earned overseas.

The bombshell development comes as Republicans probe President Biden’s role in Hunter and first brother James Biden’s foreign business dealings dating to their powerful relative’s vice presidency.

Republicans already had questioned the slow pace of a long-running criminal investigation by the US Attorney’s Office in Delaware, which reportedly is looking into Hunter over potential tax fraud, illegal foreign lobbying, money laundering and lying about drug use on a federal gun purchase form — noting that the FBI in December 2019 retrieved the first son’s abandoned laptop, which contained extensive information about income from ventures involving wealthy figures in China, Russia and Ukraine.