ROME: A scandal linking Italian Prime Minister Silvio Berlusconi with a call girl deepened Tuesday with publication of a new audio clip purportedly proving the liaison.

In the clip, the second in as many days to emerge on the website of the left-leaning weekly L'Espresso, call girl Patrizia D'Addario and the man who allegedly paid her to sleep with the prime minister purportedly discuss the terms of the encounter.

The entrepreneur, Gianpaolo Tarantini, purportedly tells D'Addario that Berlusconi "is not taking you as a call girl ... he's taking you as a friend of mine that I brought along."

Both posts followed an opinion survey that registered a four-point drop in the billionaire prime minister's approval rating, putting him below the 50 percent mark for the first time since his election in April 2008.

The poll by the IPR institute for the daily La Repubblica -- part of L'Espresso's media group -- gave Berlusconi a 49 percent approval rating, the lowest since he swept back to power for a third time since 1994.

Berlusconi's successful hosting of the Group of Eight summit this month in the earthquake-hit city of L'Aquila "may have slowed a haemorrhage that could have been much worse", La Repubblica said.

A string of scandals have dogged Berlusconi since late April.

La Repubblica has led calls for him to explain his relationship to aspiring model Noemi Letizia after his attendance at her 18th birthday party prompted his wife to file for divorce.

Allegations followed that call girls had accepted fees to spend the night with him.

Berlusconi, a renowned playboy and bon vivant, has rebuffed the allegations of paying for sex saying he prefers the "pleasure of conquest".

L'Espresso posted an audio clip on its website Monday of a purported exchange between Berlusconi and D'Addario in which he allegedly asks her to wait for him in a "the big bed" while he took a shower.

The prime minister's lawyer Niccolo Ghedini scoffed at the recording, calling it "totally implausible".

Further fueling a media frenzy, Italian authorities seized hundreds of photos taken at Berlusconi's Sardinian villa.

Some of the pictures were published in the Spanish paper El Pais and showed Berlusconi in his garden surrounded by women. Other photos showed topless women and a man who was totally nude by a pool.

The flamboyant prime minister has dismissed the allegations as "all lies" and politically motivated.

D'Addario, who is at the centre of a corruption investigation into Tarantini, has told the Italian media that she was promised 2,000 euros (2,800 dollars) for each of two sleepovers with Berlusconi.

The new audio clip refers to a 1,000 euro payment up front followed by another 1,000 if she stayed the night.

D'Addario claims to have also snapped pictures at the media tycoon's Rome residence with her mobile phone.

She says she handed the recordings over to the investigation, which does not directly implicate Berlusconi.

In the IPR poll published Tuesday, 50 percent of the 1,000 respondents said they had little or no confidence in Berlusconi, while one percent had no opinion.

It was a four-point drop from a poll in May, which credited the media tycoon with a 53 percent approval rating.