According to the report by the Darfur team, led by Nobel peace laureate Jody Williams, the situation in Darfur is "characterised by gross and systematic violations of human rights."
"Witnesses, victims and observers we met repeatedly confirmed joint action between government forces and armed militia in assaulting civilian targets in Darfur," said the report, which was commissioned in December by the U.N. Human Rights Council.
Four years of conflict between militias supporting the Arab-led government and ethnic African tribes in Darfur have resulted in at least 200,000 deaths and the displacement of about 2.5 million people, according to the United Nations.
Sudan's government is accused of supporting the militia Janjaweed, which is blamed for the conflict's worst human rights violations, including rape and torture of civilians.
The human rights team also received information about arbitrary arrests being made by government forces and "torture, inhumane and degrading treatment by national Security and Military Intelligence during attacks and in the treatment of detainees," the report said.
The report urged stronger U.N. Security Council intervention, including sanctions and criminal prosecution.
Previous efforts by the African Union and United Nations "have been largely resisted and obstructed, and have proven inadequate and ineffective," the report said.
Last month, the International Criminal Court named a Sudanese minister and a Janjaweed militia leader as the first Darfur war crimes suspects.
Sudan's government has rejected any intervention by the International Criminal Court and said it is conducting its own investigations into the conflict. The Sudanese government said it will respond to Monday's report when it addresses the council Tuesday.
The investigative team was denied access to Sudan, but met with aid agencies working in the region and African Union officials in Addis Ababa, Ethiopia.