The son of a founder of the Palestinian militant group, Hamas, Tuesday told CNN that he was a spy for Israel.

For 10 years, Mosab Yousef said he gathered information about Hamas terrorist plots and fed them to Israel's domestic security service Shin Bet.

Yousef, in an exclusive interview with CNN's Christiane Amanpour, said he did it because he came to believe that Hamas was practicing "exceptional cruelty" against its members and "killed people for no reason."

His has now written a book, "Son of Hamas" detailing his exploits from his new base in the United States where he has lived since 2007. CNN could not independently confirmed his story and Israel has refused to comment.

In the Israeli newspaper Haaretz, a former Israeli handler said of Yousef: "One insight of his was worth 1,000 hours of thought by top experts."

Yousef told CNN: "They offered me to work for them. My goal was to be a double agent and attack them from the inside."

But then his views changed.

"After I was tortured by Shin Bet I was transferred to prison [where] Hamas tortured Hamas members and I became confused who was really my enemy ... I accepted to meet Shin Bet."

Yousef said he agreed to spy on Hamas and that his decision was partly a moral one. "My people did not understand this. Shin Bet is committed to a constitution but Hamas targets civilians. There's a difference between targeting a terrorist and civilians."

He said that in part his transformation was due to spiritual reasons. "Later on, I became a Christian, during that time, the first few months, and I was convinced by the principle of loving your enemies. And I saw that my enemy, who I thought that they were my enemies, they had morality, they had their responsibilities more than my own people."

He added: "As a Shin Bet agent, when I had information I helped arrest people, otherwise they hit randomly. When I specified a particular person I had a condition - not to kill that person ...

"In 10 years working for Shin Bet I am not responsible for killing one terrorist. I care about my people, my problem was their [Hamas'] ideology.

His father, Sheikh Yousef, is serving time in an Israeli prison. He recently wrote a letter from jail saying that the whole family "inclusively and exhaustively denounce our eldest son."

An attorney for the elder Yousef obtained a statement last week from the father saying Hamas knew of his son's contact with Israeli intelligence and adding that he "was not on any day an active member in the ranks of Hamas."

Asked if he feels in danger because of what he's done, Yousef says he is not afraid. "Death is not the worst thing that can happen to a human being, physical death. The worst, spiritual and soul death. This is what really scares me."

The Israeli government, including Shin Bet, has not offered CNN official comment, and his family has broadly denied his story. But an intelligence source told Amanpour that the core claims are true, this is a "modus operandi of how Israeli agents work," to penetrate the opposite side, to try to get as much information as possible.

But the source added some of the high profile claims of thwarting terrorism or helping with high-level captures are "gross exaggerations."