A leading reformer in Sudan's ruling party should be ousted, an internal investigative committee said on Thursday, after he criticised a deadly protest crackdown.

The National Congress Party (NCP) set up the body after comments by former presidential adviser Ghazi Salahuddin Atabani and 30 other prominent party reformers.

In a memorandum to President Omar al-Bashir, they said the government's response to late-September demonstrations over fuel price hikes betrayed the regime's Islamic foundations.

The reformers made a series of recommendations, including for an independent probe of the shooting of civilians during the protests, and for a reversal of the price increases.

But they instead found themselves under investigation by the party.

Atabani's membership and that of two other signatories will be revoked if a 400-member party council gives final approval, said Ahmed Ibrahim al-Tahir, who led the internal probe.

He said six others who signed the memorandum have been suspended from party activities for one year.

Atabani, a member of parliament, told AFP on Monday that his party membership had already been suspended but the reformers would not back down.

He said the NCP was spending too much time on "this minor internal issue at a time when the country is on the verge of collapse."

Thousands of people, many of them Khartoum-area poor, took to the streets when the government cut fuel subsidies, forcing retail prices up by more than 60 percent.

Dozens were killed.