US President Joe Biden has angrily criticised an investigation into his handling of classified files which questioned his memory.

He held a surprise news briefing on Thursday evening, telling reporters: his “memory is fine.”

Special Counsel Robert Hur decided not to charge Mr Biden for mishandling files. But his report made several scathing remarks, including suggesting the president’s memory had “significant limitations”.

It said that it would be difficult to convict the president of improper handling of files because “at trial, Mr Biden would likely present himself to a jury, as he did during our interview of him, as a sympathetic, well-meaning, elderly man with a poor memory”.

Mr Biden responded that despite his age, he was the most qualified person to be president. Mr Biden’s age has become a top concern for voters going into November’s presidential election.