A top aide of Prime Minister Silvio Berlusconi involved in a corruption investigation over public contracts yesterday denied any wrongdoing, while Mr Berlusconi fiercely at-tacked the prosecutors leading the probe.

"The accusation is terrible, defamatory, I think it has been a big misunderstanding" Guido Bertolaso, well known in Italy as head of the civil protection department, said in an interview on public television.

"The fear is that Italians could feel betrayed by Guido Bertolaso, this is why I am ready to give my life to demonstrate to them that I have never betrayed them," he said.

Mr Berlusconi has repeatedly praised Mr Bertolaso for his department's response to natural disasters, including the earthquake that hit the central city of L'Aquila last April.

On Wednesday the Prime Minister rejected his offer to resign after he was put under investigation as part of a probe into contracts to build the original site intended for last year's G8 summit, later switched to a location near L'Aquila.

Mr Bertolaso, seen as a hero by many in Italy for his handling of the earthquake and other natural disasters, made no immediate comment after the probe came to light, but yesterday he responded to a public call from Mr Berlusconi to defend himself.

Mr Berlusconi, who is himself on trial for tax fraud and corruption and accuses prosecutors of waging a politically motivated campaign against him, said those investigating Mr Bertolaso "should be ashamed".

"These things are absolutely groundless and untrue, as usual," he told reporters in Brussels, where he was attending an EU summit. "We are in the presence of a barbarisation of public life which is hard to bear."

It was Mr Bertolaso who gave world leaders including US President Barrack Obama a tour of the destroyed sections of L'Aquila during last July's Group of Eight summit, which was held in a police training school in a nearby town.