Italian Prime Minister Silvio Berlusconi has blasted reports suggesting that he had a "steamy affair" with Noemi Letizia, the 18-year-old aspiring model at the heart of his divorce row, and said he would have to resign if caught lying about it.

The 72-year-old conservative leader’s relationship with Letizia created a huge furore after his wife Veronica demanded a divorce because of his womanising and said he was "not well".

In his defence, Berlusconi has denied any wrongdoing or lying, reports The Times.

His relationship with Letizia made headlines after he went to her 18th birthday and gave her an expensive necklace.

He has promised to explain it all in parliament but not set a date.

Yesterday, while in Rome, he said if someone asked whether he had "a relationship, let''s say steamy or more than steamy, with an underage girl", his answer would be "absolutely not".

"I have sworn it on the life of my children. And I said that I am aware that, if this were perjury, I would have to resign a minute later," he added.

The flamboyant media magnate has been criticised for setting a bad example to the country''s young people with his behaviour and his very public divorce.