The alleged incident is said to have taken place in London in 1967.
The Metropolitan Police said: "A man aged in his seventies was interviewed under caution by appointment at a central London location in connection with the allegation. He was not arrested."
Last week the former politician was forced to explain what he knew about concerns over suspected paedophilia in Westminster in the 1980s when he was Home Secretary.
Labour MP Simon Danczuk had called for a national inquiry into claims of historic sex abuse.
Current Home Secretary Theresa May is due to give a statement in the Commons on Monday afternoon on the issue.