Joe Biden has blamed staff for his classified documents scandal, saying they were not “thorough” enough when sorting them.

The US president also suggested that some of the “stray papers” found at his home dated from the 1970s when he was a young senator.

The discovery of dozens of classified documents, from his time as a senator and vice president, has left Mr Biden embroiled in controversy and triggered an investigation by the Department of Justice.

Some of the documents are known to have been dated between 2013 and 2016 when he was in his second term as vice president.

They reportedly included a briefing note for a phone call with a British prime minister - either David Cameron or Theresa May - and intelligence memos on issues including Ukraine and Iran.

Mr Biden gave his most detailed response on the issue in an interview with PBS NewsHour the day after he delivered the State of the Union address.

‘They didn’t do the kind of job that should’ve been done’

He said: “One of the things that happened is that, what was not done well is, as they packed up my offices to move them, they didn’t do the kind of job that should have been done to go thoroughly through every single piece of literature that’s there.

“To the best of my knowledge, the kind of things they picked up are things, they’re from 1974, stray papers. There may be something else. I don’t know.”

He added: “I’ll let the investigation decide what’s gone on, and we’ll see what happens.”

Mr Biden was elected to the Senate in 1972, becoming the youngest US senator at the time.

The first classified documents were found in an office at a think tank in Washington, which Mr Biden used after he ceased to be vice president.

That batch was discovered in a cupboard by one of his own lawyers who was clearing out the office.

More classified documents were found last month in his private library at his home in Wilmington, Delaware, and in the garage next to his Corvette.