The Sudanese authorities have given a senior government position to a man accused of co-ordinating the Janjaweed Arab militia in Darfur.
Mr Hilal blames the rebels for the deaths in Darfur
Federal Affairs Minister Abdel Basit Sabderat said clan leader Musa Hilal had been named as his adviser.
The US State Department and human rights groups say Mr Hilal is a leader of the Janjaweed, which is accused of committing war crimes in Darfur.
He denies the accusations and blames the violence on Darfur rebel groups.
More than 200,000 people have died in Darfur and two-thirds of the surviving population rely on humanitarian assistance.
'Slap in the face'
Human Rights Watch (HRW) has strongly condemned Mr Hilal's appointment.
"Musa Hilal is the poster child for Janjaweed atrocities in Darfur," said HRW's Richard Dicker.
"Rewarding him with a special government post is a slap in the face to Darfur victims and to the UN Security Council," he said, pointing out that Mr Hilal was under a UN travel ban for his role in Darfur.
Mr Hilal, an Arab clan leader, told Reuters news agency he would be based in Khartoum but might have to travel to outlying regions.
He has said he has simply mobilised Arab clans to defend against rebel attacks.
Correspondents say his appointment as a ministerial adviser will be seen as another set-back in the faltering peace process in Darfur, and is likely to increase rebel suspicions about the motivations of the authorities in Khartoum.
The International Criminal Court last year issued an arrest warrant against a junior government minister and another Arab clan leader.
The government has denied backing the Janjaweed.
There have been repeated delays in deploying a joint UN-AU peacekeeping force to Darfur, with accusations that the government is trying to block them.
Only 9,000 troops out of a planned 26,000 are currently in place.