Joe Biden’s son Hunter will now be investigated by a special counsel with additional powers, the US attorney general has announced.

Merrick Garland has elevated the status of David Weiss, the federal prosecutor who has already filed criminal charges in the case.

A plea deal on tax and gun charges against the president’s son collapsed earlier this month.

Republicans are pushing for an inquiry into Hunter Biden’s business dealings.

In a surprise announcement at the Department of Justice on Friday, Mr Garland explained that he was making the move after a request by Mr Weiss earlier this week.

The new designation will provide the prosecutor with extra resources to pursue the investigation and to potentially bring further charges beyond the state of Delaware.

Mr Garland said the special counsel would produce a report when his work was done, and that the justice department would make as much of it public as was possible.

“The appointment of Mr Weiss reinforces for the American people the department’s commitment to both independence and accountability in particularly sensitive matters,” Mr Garland said at a news conference.

Hunter Biden’s lawyer, Chris Clark, responded in a statement: “We are confident when all of these manoeuvrings are at an end my client will have resolution and will be moving on with his life successfully.”

Mr Clark pointed out that the investigation has already gone on for five years.

Hunter Biden has been charged with two misdemeanour tax offenses for allegedly not paying income taxes in 2017 and 2018, years in which he earned in excess of $1.5m (£1.1M), according to the US Attorney’s Office in Delaware.

He faces an additional felony charge for allegedly possessing a firearm while addicted to and using illegal drugs.

Hunter Biden had previously reached a deal with prosecutors to plead guilty to the tax charges and admit the gun offence to spare himself prison time.

However, US District Court Judge Maryellen Noreika squashed the deal due to “non standard terms” and the “unusual” nature of the proposed resolution for the gun charge.

Since then, Hunter Biden and prosecutors have engaged in further plea negotiations but remain at an impasse. The case is expected to head to trial.

Republicans want to see the younger Mr Biden further criminally charged, along with the president. They allege that Mr Biden has profited from his son’s business dealings in Ukraine and China.

House of Representatives Speaker Kevin McCarthy has warned that an impeachment inquiry into the president could be on the way this fall.

The White House called the allegations “insane conspiracy theories” and rejected the assertion that Mr Biden has participated in his son’s business affairs.

Mr Weiss has conducted a years-long investigation into the matter. So far, he has not found any evidence that Hunter Biden’s business dealings have benefited from his father’s presidential status.