The admission comes just days after Fairfax Media revealed the failed operation.

Fairfax alleged the Centre for Intelligence and Risk Management was responsible for the infiltration, which saw former military and intelligence officers act as anti-coal activists in order to send field reports back to CIRM.

It has since come to light that CIRM was working for C5 Management Solutions and Strongs Security Services, the same two firms Idemitsu uses for security at its Boggabri mine.

C5 Management Solutions reportedly oversaw the hiring of the private intelligence operatives, requiring them to sign non-disclosure agreements before they infiltrated the group of anti-coal protestors.

“Idemitsu has contracted Strongs Security and C5 Management Solutions to provide security services and advice," Idemitsu chief operating officer Rod Bridges told The Sydney Morning Herald.

According to the statement released by the company: “Both contracts require that these firms will carry out their services pursuant to the law and all applicable regulations”

Bridges insisted he simply “did not ask questions” as to where the security companies were getting their information from.

He told Fairfax he had little knowledge of Strongs Security despite awarding it the security contract only six months ago, though he believed it was headed by an "ex-French foreign legionnaire".

He added that he was not aware the security companies were contracting spies.

"I was pretty shocked by what I saw in the newspaper," he told reporters.

Bridges attempted to turn attention towards the protestors, pointing to the "increasingly aggressive and dangerous" actions of activists, known as the Leard Forest Alliance, which required high level security.

"These people have a right to their viewpoint. They do not have a right to break the law and put personal safety at risk for the sake of publicity and to interrupt a legitimate business,” he said.