Lord Brittan had no case to answer in relation to allegations of historical rape, a letter from Scotland Yard confirmed.
The late peer's widow, Diana, said she received the letter which stated accusations and evidence levelled at him did not amount to a case.
Operation Midland, which investigated historical claims of a Westminster VIP paedophile ring, closed last week after making no arrests and faced severe criticism.
Last month Metropolitan Police commissioner Sir Bernard Hogan-Howe apologised to Lady Brittan over the force's handling of the allegations.
Lord Brittan was accused of raping a 19-year-old woman known as "Jane" in 1967 - but the investigation was dropped when officers decided there was not enough evidence to secure a successful prosecution.
However, Lord Brittan died before knowing his name had been cleared.
Former Tory MP Harvey Proctor and ex armed forces chief Lord Bramall also had accusations lodged against them.