Mining company Idemitsu Australia Resources has admitted it contracted two companies at the centre of the extraordinary operation to use spies to infiltrate protesters opposed to the expansion of coal mining in northern NSW.

The admission follows revelations in Fairfax Media on Monday of the clandestine but bungled operation. Several of the private intelligence operatives were uncovered by the activists.

Idemitsu's Rob Bridges.

As revealed on Monday, the Centre for Intelligence and Risk Management handled the infiltration, in which former military and intelligence officers pretended they were anti-coal activists, sending field reports back to CIRM about what they saw and heard.

It has since emerged that CIRM was working for C5 Management Solutions, a Canberra-based security consultancy headed by former Australian Federal Police officer Tyrone Clark.