An attack on the late Pope John Paul II in Portugal by a deranged Spanish priest in 1982 that wounded the pontiff was kept secret, according to Cardinal Stanislaw Dziwisz, his former secretary.

Cardinal Dziwisz, now Archbishop of Krakow, has made the disclosure in a documentary entitled "Testimony" to be shown at the Vatican tonight (Thursday) in the presence of Pope Benedict XVI.

The cardinal says the attack occcured on 12 May 1982 while the then Pope was visiting the Marian shrine at Fatima in Portugal to give thanks to the Virgin Mary for saving his life during an assassination attempt a year earlier, when he was shot in St Peter's Square by the Turkish right wing gunman Mehmet Ali Agca.

During the Fatima ceremony a right wing Spanish priest, Juan Fernandez Krohn, attacked the pontiff with a dagger. The priest was tackled by police and disarmed. The event was reported at the time but downplayed, and the fact that the Pope was injured was suppressed. "I can now reveal that the Holy Father was wounded" Cardinal Dziwisz says. "There was blood".

Father Krohn was arrested and served a sentence in a Portuguese prison before being expelled. The documentary, narrated by the actor Michael York, also includes John Paul II's final public appearance from his study window above St Peter's Square three years ago when he was unable to speak.

Cardinal Dziwisz says that the Pope, who had undergone a tracheotomy to help him breathe, whispered to aides "If I cannot speak any more, it is time for me to go". He died shortly after Easter, on 2 April 2005.

The documentary "will ensure that John Paul II is not forgotten," Cardinal Dziwisz told a press conference. adding that the late Pope had been "like a father to me." The film is partly based on Cardinal Dziwisz's memoir "A Life with Karol" and was directed by the Polish filmmaker Pawel Pitera.