THE Australian Federal Police is keeping secret the advice it relied on to shut down a criminal inquiry into AWB's payment of kickbacks to Iraq, claiming legal professional privilege.

The AFP's refusal of a freedom-of-information request from The Age for advice provided by Peter Hastings, QC, comes after former senior federal agent Rosario Fusca, alleged a colleague told him he would be promoted if he could ''make the Oil for Food taskforce go away''.

The taskforce was established in late 2006 and given a $30 million budget after Commissioner Terence Cole found 11 former AWB executives and a British-based former BHP manager may have committed criminal offences by knowingly allowing the company to make $300 million in illicit payments to Saddam Hussein's regime in breach of United Nations sanctions.

When the taskforce was shut down in August 2009, the then AFP commissioner, Mick Keelty, said the decision was partly based on advice given by Mr Hastings, who warned that a criminal prosecution of former AWB managers was unlikely to be successful.

In refusing to release Mr Hasting's 39 pages of advice, the AFP said the documents were ''brought into existence for the purpose of obtaining legal advice and for use in litigation''.

An AFP spokesman said it had not waived its right to hold privilege over Mr Hastings' advice, despite shutting down the taskforce.

Mr Fusca, who served as the acting co-ordinator on the Oil for Food taskforce, is suing the AFP in the Federal Court under the Fair Work Act.