In his first publicly aired remarks since he was arrested nearly a fortnight ago over Austria's worst recorded multiple rape and incest scandal, Fritzl, 73, said that media coverage of the case had been "unfair and entirely one dimensional".

Speaking through his lawyer, Rudolf Mayer, who visited him in prison, Fritzl said: "I am no monster, I could have killed all of them and no one would have known. No one would ever have found out about it."

Fritzl locked his daughter Elisabeth in a bunker beneath his home in the Lower Austrian town of Amstetten when she was 18 and raped her every three days on average. Seven children resulted from the incestuous relationship.

Three of them, Kerstin, 19, Stefan, 18, and Felix, five, spent their entire lives underground with their mother. They did not see daylight until they were freed from the cellar last month when Fritzl allowed Kerstin to be taken to hospital after she lapsed into a coma.

Fritzl claimed in his statement that he had saved his daughter's life. "Kerstin would not be alive today if it wasn't for me," he told his lawyer. "I made sure that she got to hospital."

State prosecutors interviewed Fritzl in prison for the first time since his arrest yesterday.

He is due to appear in court tomorrow during a closed session that is almost certain to rule that he remain in custody until his trial.

Mr Mayer claims that his client is suffering from diminished responsibility and should not go to prison if found guilty. "He belongs in a closed psychiatric unit and not in jail," he said in an interview.

The Austrian authorities admitted for the first time yesterday that they had been naïve in accepting Fritzl's story that his daughter had run away to join a religious cult when she was, in fact, being held prisoner in his cellar.

Maria Berger, the Interior Minister, said that police and social services had acted "somewhat gullibly" over the case.

"Today, we would surely go about it differently and conduct a detailed investigation," she added.

The Austrian government has said it will consider doubling the period for which rape offences are held on criminal records. It emerged last week that Frtizl had been convicted of rape and jailed for 18 months in the 1960s, but that, in accordance with current Austrian law, the offence was expunged from criminal records after 15 years.