Long-standing concerns over US President Joe Biden’s age and memory intensified following the release of a special counsel’s report investigating his possession of classified documents.

The report, which was published on Thursday, described the 81-year-old Democrat’s memory as “hazy”, “fuzzy”, “faulty,” “poor” and having “significant limitations.”

It noted that Mr Biden could not recall defining milestones in his own life.

“He did not remember when he was vice president, forgetting on the first day of the interview when his term ended (‘if it was 2013 — when did I stop being Vice President?’), and forgetting on the second day of the interview when his term began (‘in 2009, am I still Vice President?’),” the report said.

“He did not remember, even within several years, when his son Beau died.”

While Mr Biden will not face charges for mishandling classified documents, the report’s assertions about his memory could undermine his message to voters that he can manage the government and safeguard the country.

Voters are already going into this year’s election with severe misgivings about the president’s age having scrutinised his gaffes, coughing, slow walking and even a summer tumble off his bicycle.

In ruling out a prosecution of Mr Biden over his retention of highly classified materials as a private citizen, the report suggested he would seem too feeble to prosecute: “It would be difficult to convince a jury that they should convict him — by then a former president well into his eighties — of a serious felony that requires a mental state of wilfulness.”

The White House pushed back on the characterisations of Mr Biden’s memory in a letter from the president’s lawyers that was published in special counsel Robert Hur’s report.

The letter argues that Mr Biden’s “inability to recall dates or details of events that happened years ago is neither surprising nor unusual,” particularly about when certain documents were packed or moved.

“We do not believe that the report’s treatment of President Biden’s memory is accurate or appropriate,” the letter said.

“The report uses highly prejudicial language to describe a commonplace occurrence among witnesses: a lack of recall of years-old events. Such comments have no place in a Department of Justice report.”

It is not unusual for the subjects of government investigations to say they don’t recall an event or a conversation in order to avoid issues such as perjury.

The special counsel did not release the transcript of the interviews with Mr Biden, so some context is unclear.

Former president Donald Trump, the current Republican front-runner, has boasted of his own vast memory but has also at times said in legal proceedings that he does not recall certain events.

Mr Biden noted in a statement issued on Thursday that he had sat for five hours of interviews with Mr Hur’s team over two days on October 8 and 9, “even though Israel had just been attacked on October 7th and I was in the middle of handling an international crisis”.

In an August poll by The Associated Press-NORC Centre for Public Affairs, 77% of US adults said Mr Biden is too old to be effective for four more years.

It was one of the rare sources of bipartisan agreement during a politically polarised era, with 89% of Republicans and 69% of Democrats saying Mr Biden’s age is a problem.

The release of the report overlapped with recent Biden speeches in which he mistakenly claimed to talk with European leaders — France’s Francois Mitterand and Germany’s Helmut Kohl — who had not held office since the 1990s and in fact had died several years ago.