Prime Minister Benjamin Netanyahu ordered the Shin Bet security service a few months ago to investigate senior members of his bureau suspected of passing sensitive information to the media, Army Radio reported on Thursday.

Netanyahu's suspicions were aimed at some of his closest aides and he thus made a personal request to the Shin Bet and to Attorney General Yehuda Weinstein to look into the matter, according to the report.

The suspected culprits included National Security Adviser Uzi Arad, Cabinet Secretary Zvi Hauser, former Prime Minister's Bureau spokesman Nir Hefetz and other senior figures. They were each questioned by the Shin Bet and underwent a polygraph test.

In response to the report, the Shin Bet said that the suspected violations had proved to be mere speculation. No sensitive information had been leaked by any members of the Prime Minister's Bureau, said the Shin Bet. The results of the investigation have all been passed on to the attorney general, added the Shin Bet.

The Prime Minister's Bureau issued a statement denying the report, saying that Netanyahu solely instructed the Shin Bet to examine how "information crucial to the state's security" was leaked.

"The decision of who will be investigated and in what ways was the professional decision of the Shin Bet. The prime minister did not intervene in the investigation in any way," the statement said.

Netanyahu's bureau also emphasized that the Shin Bet decided to investigate several people outside the bureau who were also privy to important information.

Hefetz announced last week that he was quitting his position as media adviser, 18 months into the job, become the third Netanyahu aide to quit in a matter of days. In resigning, Hefetz joined political adviser Shalom Shlomo and personal aide Tzachi Gavrieli, who had also worked in the Prime Minister's Bureau under Ariel Sharon.

Hefetz informed Netanyahu of his intention to step down three weeks ago following a Gidi Shmerling, who had been Jerusalem Municipality spokesman, and deputy to Hefetz during the past six months, took over Hefetz's post.