Silvio Berlusconi, the Italian Prime Minister, has faced renewed criticism from the Roman Catholic Church over his links to Noemi Letizia, 18, a model from Naples.

Mr Berlusconi, 72, is said to be alarmed by the possible impact of the affair on the Catholic vote in next month’s European elections.

Alessandro Plotti, former Archbishop of Pisa and former vice-president of the Italian Bishop’s Conference (CEI) said: “Matters that so heavily involve the private life of a head of state cannot but harm his personal credibility.”

As the CEI held its annual general assembly in Rome the archbishop, a senior and respected voice in the Church, said that the “media storm” surrounding the case risked “transforming immoral choices into signs of success, examples of a power that allows itself to do anything.”

He told La Stampa that “the deadly trickle of details and indiscretions adding to the general picture is alarming. People with responsibility, people who hold public roles at the highest levels cannot ignore the way that their actions and the way they explain themselves to others have an effect on public opinion.”

He added: “This scandal shows how dramatically the level of public morality has sunk. . . Things become normal which most certainly are not.” He said that those in power should be examples of “austerity, sobriety, and a life ruled by self-control”. If the scandal was not got up by the press “which frankly I hope it is”, it would lead to “terrible results we cannot imagine”.

Father Antonio Sciortino, editor of the popular Catholic weekly Famiglia Cristiana, said Italy had had enough of “a culture of showgirls and TV hostesses. The country needs something quite different. It has to tackle the problems of the grave economic crisis it faces. But it is up to the Prime Minister to clear things up once and for all. One cannot refuse legitimate questioning from the media. No one can claim moral immunity. Everybody is required to account for their own behaviour. Even the slightest doubt that he has lied must be removed.”

Mr Berlusconi’s attendance at Ms Letizia’s 18th birthday party in a Naples suburb last month led Veronica Lario, his wife, to demand a divorce. She said: “I cannot stay with a man who frequents minors.”

In an interview with CNN, the television news channel, Mr Berlusconi said: “They accuse me of lying? Fine, I will react, I will explain exactly what the situation is, and once more all the Italians will be with me.” He said that there was “nothing, but nothing, even minimally negative” about his relations with Ms Letizia, which were “part of my private life”.

Benedetto Letizia, her father, said that he had first got to know Mr Berlusconi at an election meeting in 2001, and at Christmas the same year had presented Anna, his wife, and daughter Noemi, then ten, to Mr Berlusconi, who had expressed sympathy over the loss of their son Yuri, who died in a car crash. He said Mr Berlusconi had said to his daughter “look on me as your grandfather”. She had told him she preferred to call him “Papi” (Daddy).

Mr Berlusconi said that he was considering addressing Parliament about his links to Ms Letizia to clear his name. “A lot of people should be ashamed of what they have said and written,” he said.

Dario Franceschini, leader of the opposition Democratic Party, called on him to respond to questions immediately. “It is not possible that the free press continues to ask questions, continues to show where he has lied and he continues to stay silent,” he said.