Pope John Paul II whipped himself with a belt and slept on the floor as acts of penitence and to bring him closer to Christian perfection, according to a new book.

The book by the Polish prelate spearheading his sainthood case Why He's a Saint also includes previously unpublished speeches and documents written by John Paul, including one 1989 signed memo in which he said he would resign if he became incapacitated.

The book also reported for the first time that John Paul forgave his would-be assassin in the ambulance on the way to the hospital moments after he was shot on May 13, 1981, in St Peter's Square. And it reported that he initially thought his attacker was a member of the Italian terrorist organisation the Red Brigades.

The book was written by Monsignor Slawomir Oder, the postulator, or main promoter, for John Paul's canonisation cause and was released today. It was based on the testimony of the 114 witnesses and boxes of documentation Oder gathered on John Paul's life to support the case.

Today Mgr Oder defended John Paul's practice of self-mortification, which some faithful use to remind them of the suffering of Jesus on the cross.

"It's an instrument of Christian perfection," he said, responding to questions about how such a practice could be condoned considering Catholic teaching holds that the human body is a gift from God.

In the book Mgr Oder wrote that John Paul frequently denied himself food - especially during the holy season of Lent - and "frequently spent the night on the bare floor," messing up his bed in the morning so he wouldn't draw attention to his act of penitence.

"But it wasn't limited to this. As some members of his close entourage in Poland and in the Vatican were able to hear with their own ears, John Paul flagellated himself. In his armoire, amid all the vestments and hanging on a hanger, was a belt which he used as a whip and which he always brought to Castel Gandolfo," the papal retreat where John Paul vacationed each summer.

While there had long been rumours that John Paul practised self-mortification, the book provides the first confirmation and concludes John Paul did so as an example of his faith.

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