Defectors from the Islamic State (ISIS) are condemning the leadership of the jihadist group, saying they are killing Muslims instead of protecting them.

Prof. Peter Neumann, the director of the International Centre for the Study of Radicalisation (ICSR) at King's College in London, said this was one of the findings made in a study conducted by ICSR, according to CNN.

The study, called "The Narratives of Islamic State Defectors,'' said the ISIS defectors—described as a "new and growing phenomenon"—could become potential partners in "stopping the flow of foreign fighters, countering the Islamic State's propaganda and exposing their lies and hypocrisy."

ICSR encouraged governments and civil society to make it easier for these defectors to speak out without the threat of prosecution by assisting them and recognising their value in the global fight against terrorism.

"Not every defector is a saint, and not all of them are ready or willing to stand in the public spotlight. But their voices are strong and clear: 'The Islamic State is not protecting the Muslims. It is killing them.' They need to be heard,'' Neumann said.

He said whenever possible, "governments should assist them in resettlement and ensure their safety. They also need to remove legal disincentives that prevent them from going public.''

ICSR said since January 2014, at least 58 fighters have left ISIS and publicly spoken about their defection. From June to August, at least 17 fighters were reported to have defected.

Many of those who shared their stories said they were disaffected by the killing of fellow Sunni Muslims, including innocent civilians and the failure to confront the regime of President Bashar Assad, according to CNN.

Most of the group's attention was consumed by quarrels with other rebels and the leadership's obsession with "spies" and "traitors," according to the report.

Syrian defectors disapproved of the conduct of individual commanders and "emirs.'' They criticised the privileges given to foreigners, for which they claimed was not justifiable based on the group's philosophy or Islam in general.

A defector from India, whom the group reportedly forced to clean toilets because of his skin colour, complained about unfairness, inequality and racism.

Most of the defectors said they joined the group for "selfish'' reasons but found out later that life under ISIS was harsh and disappointing.

Some described their duties as "dull'' and complained about the lack of deployments. One defector claimed that foreign fighters were "exploited" and used as cannon fodder.

ICSR said none of the narratives mentioned involved minorities. It likewise noted that ISIS brutality "didn't seem to be a universal concern" and that it was "seen through a sectarian lens, and caused outrage mostly when its victims were other Sunnis."

Despite some inaccuracies in the defectors' testimonies, ICSR concluded there was "consistency" in their messages. "These stories matter...Their example may encourage others to follow, and their credibility can help deter wannabes from joining,'' it said.

ICSR said the defectors are now permanent residents in 17 countries, including nine in Western Europe and Australia.