Berlusconi, 73, is due to have a 'working dinner' with David Cameron on Wednesday and the two will then give a joint press conference - with aides of the Italian fearing potentially embarrassing questions.
Last summer the media tycoon was embroiled in a scandal when it emerged escorts had been among guests invited to parties he had hosted at his official residence in Rome.
Escort Maria Teresa De Nicolo (right) has alleged she shared a bed with Italian Prime Minister Silvio Berlusconi and two other women
Today a statement to prosecutors by escort Maria Teresa De Nicolo, 38, known as Terry, was published by Italian newspaper La Repubblica which revealed the group sex claim.
Ms De Nicolo's involvement in the parties last year was known but her claim that she and two other escorts were in bed with Berlusconi had not been known.
In her statement she said: 'In the bed there was me, two girls from Rome and Berlusconi,' she added how the scene had unfolded at Berlusconi's Palazzo Grazioli residence in Rome.
Ms De Nicolo had been invited to the party by businessman Gianpaolo Tarantini, who is at the centre of a corruption probe in his hometown of Bari in southern Italy.
Details of escorts attending Berlusconi parties emerged after intercepted telephone calls between Tarantini and others were leaked in which he spoke of the girls.
Ms De Nicolo described how Tarantini had called her and given her 30 minutes notice to get ready for a flight from Bari to Rome and that he had said: 'Tonight we are going to dinner with Berlusconi.'
She added: 'I thought it was a joke. Then he gave me the details and told me to "dress sexy".'
In her statement she described how she was driven to Palazzo Grazioli and was surprised at the lack of security.
Last year, escort Patrizia D'Addario claimed she had also spent the night with the Prime Minister
Ms De Nicolo said there were 'fifteen girls' at the party and she added that at the evening Tarantini had 'made it clear he wanted me to stay the night.'
She went on: 'I spent some hours sleeping alone and some hours with the girls, these two from Rome and Berlusconi,' before adding that when she left the next morning he had given her jewellery as a gift.
Her statement also added how Tarantini had given her 1000 euros as well as paying for her travel expenses.
Last year another escort Patrizia D'Addario, 43, revealed how she had also spent the night with Berlusconi and she later released a tape in which he told her to 'touch herself' during sex.
Ms D'Addario later published a book in which she recounted her time at Palazzo Grazioli and praised Berlusconi for his sexual stamina saying he 'deserved a place in the Guinness Book of Records.'
Today there was no-one immediately available at Berlusconi's office to comment on the claims, which also come ahead of a confidence vote on junior justice minister Giacomo Caliendo who has been questioned as a corruption probe.
Berlusconi has also lost his majority in parliament after he threw his Party of Freedom ally Gianfranco Fini out of his party pushing his centre right government coalition to the brink of crisis. ( dailymail.co.uk )