The Republican-controlled US House Oversight Committee said on Wednesday it has subpoenaed President Joe Biden's son, Hunter Biden, and brother, James Biden, to appear for depositions, in an escalation of its impeachment inquiry into the Democrat.

House Republicans launched an impeachment inquiry in September, following months of probes. They allege that Biden and his family have personally profited from policy decisions Biden made when he was vice president during former President Barack Obama's administration.

Neither Hunter Biden nor James Biden could immediately be reached for comment.

Devon Archer, a former business associate of Hunter Biden, told lawmakers in a closed-door interview that the younger Biden sought to create "an illusion of access to his father" and put his father on the phone with foreign associates "maybe 20 times" over the course of Archer's business relationship with Hunter Biden. Archer's testimony was later publicly released.

White House press secretary Karine Jean-Pierre on Wednesday referred reporters to the Bidens' "personal representatives" for specific questions, but called the investigation a "smear campaign." The investigation "has gone on for a year now and has turned up zero evidence against the president," she said.

The impeachment inquiry has been publicly supported by former President Donald Trump, who is the frontrunner for the Republican nomination to take on Biden in the 2024 election.

In addition to the subpoenas to Hunter Biden and James Biden, the committee is issuing a subpoena to Rob Walker, a former business partner of Hunter Biden.

The committee is also asking four other members of Biden's family to appear, as well as another former business partner, Tony Bobulinski. The committee said it would send additional subpoenas and interview requests later in the week.

The committee has previously received financial records for members of the family. (Reuters)