A senior Pentagon official broke government rules and lied to superiors when he set up an "unauthorised" network of private contractors to spy in Afghanistan and Pakistan, an internal probe has found.

The investigation stated that the high-ranking intelligence expert set up the network starting in late 2009 and "deliberately misled" top generals about it, according to a Pentagon spokesman who summarised the classified report on Friday.

"These policy violations consisted of directing unauthorised HUMINT operations conducted by non-government personnel under the guise of gathering and reporting "force protection atmospherics" for the 'Information Operations CAPSTONE'," a human intelligence gathering project, Pentagon spokesman David Lapan said.

The results of the defence department investigation, ordered by defence secretary Robert Gates after The New York Times reported on the network's existence in March, are classified.

Mr Lapan said the probe concluded that "further investigation is warranted of the misleading and incorrect statements the individual made" about the legality of the program.

The New York Times identified the official in question as Michael Furlong, a senior official at the Joint Information Operations Warfare Centre, which integrates information such as intelligence into military planning.

Pentagon rules forbid using contractors as spies and the newspaper said some of the information provided by the network was used for strikes against militants.

Furlong's network was made up of small companies - including one run by an ex-CIA agent - that used agents in Afghanistan and Pakistan to gather intelligence on militant groups.

It operated under a $22 million contract run by US technology giant and defence contractor Lockheed Martin, according to the Times.

Furlong told the newspaper his work had been approved by a number of senior military officers in Afghanistan, and that he misled no one. He also said he was never interviewed by the defence department as part of the inquiry.

The New York Times reported that the Air Force inspector general is conducting a separate probe to see if Furlong broke any laws or committed contract fraud.

Atmospherics are generally understood to be the environmental, security, political, and socio-cultural gauges that a military analyzes as part of a broader assessment of a conflict zone.

Lapan said the inquiry recommended adding "a definition of 'atmospherics' and an expanded definition of HUMINT that ensures no ambiguity between HUMINT and atmospherics can occur."

- AFP