Former US President Bill Clinton and his wife Hillary Clinton, the former Secretary of State, have agreed to testify in the congressional investigation into late sex offender Jeffrey Epstein.

Bill Clinton's deputy chief of staff confirmed the news on social media, writing: "The former President and former Secretary of State will be there."

It comes as the Republican-led US House of Representatives was preparing to vote on holding both Clintons in criminal contempt for defying legal summonses.

Bill Clinton's photo appears in Epstein files released by the Department of Justice, although the former Democratic president has denied any wrongdoing.

It will be the first time a former US president has testified to a congressional committee since Gerald Ford did so in 1983.