The US Federal Bureau of Investigation suspected one of President Lyndon B Johnson’s closest aides was gay and persuaded him for the need to find out, it has emerged.

Documents published in the Washington Post show the extent to which FBI Director J Edgar Hoover used his power to find out information about the sex lives of influential Americans.

Jack Valenti was targeted by the FBI soon after he left his job as an ad executive in Houston to serve as an aide to President Johnson.

“J Edgar Hoover’s FBI found itself quietly consumed with the vexing question of whether Valenti was gay,” according to the Post.

The President initially blocked the Bureau from investigating his friend or questioning him about his sexuality.

Mr Valenti was married in 1962 and later had three children. He became an important Washington figure after his two years at the White House as president of the Motion Picture Association of America.

He was with Johnson in Dallas as he was sworn in as President after the assassination of John F Kennedy and travelled back to Washington with him.

As such he was one of Johnson’s closest advisers and confidantes from the first moments of his Presidency.

“Previously confidential FBI files show that Hoover’s deputies set out to determine whether Valenti, who had married two years earlier, maintained a relationship with a male commercial photographer,” reports the Post.

“Republican Party operatives reportedly were pursuing a parallel investigation with the help of a retired FBI agent, bureau files show. No proof was ever found, but the files, obtained by The Washington Post under the federal Freedom of Information Act, provide further insight into the conduct of the FBI under Hoover, for whom damaging personal information on the powerful was a useful tool in his interactions with presidents from Franklin D. Roosevelt to Richard M. Nixon.”

As Director of the FBI and its predecessor from 1924 to 1972, he wielded unparalled powers to influence and blackmail senior figures.

He was also widely suspected of being gay, and lived with his “life partner” Clyde Tolson for decades.

Mr Tolson, an associate director of the FBI who was also Mr Hoover’s heir.

Another Johnson aide was forced to resign in Ocotber 1964 after it emerged he was a homosexual.

Walter Jenkins had worked closely with Johnson since 1939, but when he was arrested by police in Washington DC performing oral sex on a man in a YMCA bathroom he had to resign. 

The loss of one of his most loyal aides was a serious blow to the President, who split up his duties rather than replace him.

Journalist Bill Moyers, a former Johnson aide, said in 1975:

“When they came to canonise political aides, [Jenkins] will be the first summoned, for no man ever negotiated the shark-infested waters of the Potomac with more decency or charity or came out on the other side with his integrity less shaken. If Lyndon Johnson owed everything to one human being other than Lady Bird, he owed it to Walter Jenkins.”