Geneva: Serious crimes committed by former rebels in Libya risk going unpunished because members of the UN's top human rights body show little appetite to press the new government to investigate abuse committed since the fall of the Muammar Gaddafi regime, rights groups warned on Wednesday.

A UN expert panel report published earlier this month found former rebels continue to persecute people perceived as loyal to Gaddafi. Militias are holding thousands of people in makeshift detention where torture is rife, the report said.

"The transitional authority is not willing to investigate what these militias are doing," said Donatella Rovera, senior crisis response adviser at Amnesty International.

"They are not even willing to admit the extent of the problem. For those people who are victims of the militias they have nobody to turn to," she said.

Rovera said campaigners were disappointed that a resolution to be voted on this week by the UN Human Rights Council lacks any concrete proposals for investigating abuses.

The resolution before the Geneva-based body was submitted by the new government itself and is titled ‘Assistance for Libya in the field of human rights'.

Elham Saudi, the director of the London-based group Lawyers for Justice in Libya, said the council risks rewarding the new government with impunity in much the same way as Gaddafi was embraced by the international community after he gave up his nuclear programme and took responsibility for the Lockerbie attack that killed 270 people on Pan Am Flight 103.

"They [the new government] have said the right things and made the right noises but they haven't really changed anything," she said.