JERUSALEM (Reuters) - A Hamas leader's son who spied on the movement for Israel, and then wrote about his exploits while in exile, has turned his sights on the religion of his father.

On a rare visit to Jerusalem, just a short car ride from the family that disowned him in the occupied West Bank, Mosab Hassan Yousef told journalists he was making a film about the Prophet Mohammad that would reveal his "real nature" to Muslims.

"This is time to free people from the absolute control of religion, by reasoning, by a better understanding," he told a news conference. It turned testy as he was challenged on his assertion that Islam was a "religion of war" compared to other major faiths, and his defense of contentious Israeli policies.

Yousef secretly converted to Christianity and helped the Shin Bet security service in the late 1990s and early 2000s, when Hamas waged suicide bomb campaigns against Israel. He was codenamed "Green Prince" after the Islamist color and the fact that his father, Hassan Yousef, led Hamas in the West Bank.

Now 34, Yousef unmasked himself in a 2010 book, "Son of Hamas", and has been living in refuge in the United States.

He stayed in touch with his Shin Bet handler and makes no apologies for actions which, in the eyes of many Palestinians, make him a traitor and apostate deserving of death.

"Usually people are ashamed when they do something wrong. People love to live in the darkness ... I live in the light. I didn't do anything wrong by saving human life," he said in at the Jerusalem event hosted by Media Central, a pro-Israel press relations organization.

The Shin Bet declined comment, but two retired senior officers told Reuters that Yousef's account of his double life as a spy and trusted lieutenant to his father was largely true.

Family unforgiving

In his book he asserted that he foiled Palestinian attacks and also arranged for the elder Yousef to be repeatedly arrested in order to spare him assassination by Israel.

The Hamas leader, in Israeli custody again, issued an angry statement to Palestinian media reaffirming that he had shunned his son. Yousef's mother, Subha, was similarly unforgiving.

"I'm not to be addressed as his mother because he's not my son. He gave his loyalties to a religion other than Islam. We're Muslims and he attacked our religion," she told Reuters. "He didn't save anyone. These are myths in his own head."

Watchful and lean in a trim gray suit, Yousef exuded the air of a revival preacher as he railed against political Islam and its spread in the Middle East, citing the ascendancy of Hamas' kindred Muslim Brotherhood in Egypt.

He said there had been "hundreds of thousands of downloads" of the Arabic version of his book, available online for free. But he declined to answer a journalist who addressed him in Arabic and, while praising Israeli democracy, had little time for a question about whether Jewish settlement on land where Palestinians seek independence was consistent with his values.

"I think Palestinians need freedom and human rights more than they need a state," he said, calling for the emancipation of women, security for homosexuals and freer religious debate.

Yousef said he has also been making a screen version of his book along with Sam Feuer, an Israeli producer based in Beverly Hills. They said their Mohammed biopic already has an actor cast for the lead - though they would not name him - and funding.

Many Muslims consider any depiction of the Prophet Mohammad to be deeply blasphemous. Feuer struck a conciliatory note, saying the film about Islam's founder could prove illuminating.

"It's not just a movie for Muslims to learn about Islam themselves, what they cherish, but also for people who aren't from Islam to learn the true culture and history of the religion," he said.