Two panels in the Republican-controlled US House of Representatives have backed holding Attorney General Merrick Garland in contempt of Congress.

The House Judiciary and Oversight Committees made their recommendations after Mr Garland advised President Joe Biden to defy their legal demands.

Republicans had demanded the release of audio tapes from a probe of Mr Biden's handling of classified documents.

The findings have raised questions about the president's memory and age.

The Judiciary Committee's 18-15 vote and the Oversight Committee's 24-20 vote took place on Thursday entirely along partisan lines.

Their actions advance the contempt resolution against Mr Garland to the full House chamber, which means that the country's top prosecutor could face a potential criminal referral.

The effort to hold the US attorney general in contempt stems from a 345-page report released by Special Counsel Robert Hur in February, the result of a year-long inquiry into Mr Biden retention of classified documents after leaving the vice-presidency in 2017.

The Garland-appointed prosecutor said that no criminal charges against Mr Biden were warranted, despite the 81-year-old "willfully" retaining classified materials as a private citizen.

Mr Hur's report noted that the special counsel believed prosecutors would struggle to secure a conviction against Mr Biden, as jurors would likely view him as a "well-meaning, elderly man with a poor memory".

That characterisation came after the president sat through five-hour interviews across two days last October with Mr Hur's team. The report says that Mr Biden was unable to recall certain details relevant to the investigation.

Mr Hur, a Republican, recounted that Mr Biden had also struggled to recall milestones in his own life, including the years of his vice-presidency and when his oldest son Beau had died from cancer.

The report's release was a difficult moment for Mr Biden and his fledgling reelection campaign. It immediately stressed one of Mr Biden's biggest political weaknesses - voter concerns about his age and lucidity.

The White House and many Democrats have pushed back on Mr Hur's characterisation, alleging that the special counsel's claims went beyond the scope of his appointment and were misleading.

"I'm well-meaning, and I'm an elderly man. And I know what the hell I'm doing," the president said angrily at an impromptu press conference.