After a chaotic four hours, Hunter, in a pro forma move, pleaded not guilty to the allegations against him.

The dramatic developments are a blow for the White House, which had been hoping this would be the end of a five-year investigation that began when Donald Trump was still in office.

For years, Republicans have accused Hunter of leveraging his father’s political power for personal and financial gain, but have not been able to prove this. The plea deal, which was made last month as Trump faced his own legal woes, was particularly contentious because critics viewed it as yet another example of a “two-tiered” justice system under the Biden administration.

But as the case has become increasingly politicised, House Speaker Kevin McCarthy this week floated the idea of a Biden impeachment inquiry – something Trump loyalists have wanted for months – saying it “allows Congress to get the information to be able to know the truth” about Hunter’s business dealings and whether his father was connected to them.

Tensions intensified in recent weeks, after whistleblowers claimed the Department of Justice (DoJ), the FBI and the Internal Revenue Service had interfered in the tax evasion probe against Hunter.

Among them was IRS agent Gary Shapley who told Congress and conservative news stations that decisions in the case appeared to be “influenced by politics”, from “slow-walking investigative steps” to “limiting investigators’ line of questioning for key witnesses”.

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In a particularly explosive allegation, Shapley also said the IRS obtained a WhatsApp message dated July 30, 2017, from Hunter Biden to Henry Zhao – a Chinese Communist Party official and chief executive of Beijing-based firm Harvest Fund Management.

“I am sitting here with my father and we would like to understand why the commitment made has not been fulfilled,” the text message purportedly said. “Tell the director that I would like to resolve this now before it gets out of hand, and now means tonight.”

To Republicans, the WhatsApp message looked like a shakedown and gave weight to their claim that the Biden family was engaged in influence peddling and corruption. Hunter’s lawyers, however, dismissed it as a fake.

McCarthy said “Hunter Biden got a sweetheart deal from his dad’s DoJ.” Speaking at Capitol Hill, he told reporters: “The more this continues to unravel, it rises to the level of an impeachment inquiry. What that simply provides is that the American public has a right to know, and it allows Congress to get to the information to be able to know the truth.”

An impeachment inquiry by the House of Representatives would be a first step towards bringing articles of impeachment against Joe Biden, just as Trump faced two impeachments during his four years in office.

Such a probe could be as lengthy as the House determines, potentially stretching into the 2024 campaigning season, which is shaping up to be a rematch between Trump and Biden.

Trump, however, faces a myriad of legal problems of his own, including looming court cases for alleged hush money payments, mishandling of classified documents, and another civil trial against writer E. Jean Carroll, who he was recently found to have sexually abused and defamed.

Joe Biden did not have any public engagements on Wednesday and has not commented on his son’s case. But the 80-year-old is fiercely protective of Hunter, a recovering drug addict, and often keeps him close.

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Speaking to reporters at the White House, press secretary Karine Jean-Pierre noted that “this case was handled independently, as all of you know, by the Justice Department under the leadership of a prosecutor appointed by the former president, President Trump”.

“Hunter Biden is a private citizen, and this was a personal matter for him,” she said.

“As we have said, the president, the first lady, they love their son, and they support him as he continues to rebuild his life.”

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