U.S. Rep. Ken Buck has asked the Department of Justice to appoint a special counsel to investigate an allegation of impropriety against the son of President-elect Joe Biden.

“This investigation is critical to defending the integrity of the republic and ensuring a potential Biden Administration will not be the subject of undue foreign influence,” Buck wrote on Monday in a letter to Attorney General William Barr. “Americans have the right to know whether Mr. Biden’s reported ties to foreign governments will make him the subject of blackmail attempts or other nefarious efforts to undermine U.S. national security or otherwise improperly influence foreign policy.”

As The Washington Post reported in October, claims that a laptop belonging to Hunter Biden showed he arranged a meeting with a Ukrainian energy executive when his father was vice president remain independently unverified. The source material originated from Rudolph Guiliani, President Trump’s personal lawyer who, since the election, has challenged the results of the presidential vote in numerous states.

Buck, the former Weld County district attorney who is also the chair of the Colorado Republican Party, has not called for similar investigations into the family of Trump, even though special counsel Robert S. Mueller looked into Donald Trump Jr. for his 2016 meeting with a Russian national promising “dirt” on Hillary Clinton. New York Attorney General Letitia James sought testimony and documents from Eric Trump in a financial investigation.

In October 2019, Buck also voted against beginning an impeachment inquiry into Trump over the president’s attempt to solicit Ukrainian interference in the 2020 election to damage Biden.

“It’s all hearsay and speculation and it’s time for the House to return to legislating for those who sent us to Washington,” Buck said at the time.