Silvio Berlusconi, the Italian Prime Minister, who is already fighting to avoid imminent trials for tax evasion and bribery, was dealt a further blow today when Veronica Lario, his estranged wife, announced that she was taking him to court in a divorce battle.

At stake is his fortune, estimated at between 5 billion and 8 billion euros (£4.5 billion and £7 billion). It is not yet known whether Ms Lario's divorce action includes a specific demand over the division of his legacy. But Corriere della Sera said experts on inheritance and business law had been included in Ms Lario's legal team, and his business empire would be the crux of the case.

Me Berlusconi, 73, has been seeking a discreet out-of-court settlement with Ms Lario, 53, since she declared she was leaving him six months ago over his relationships with other women. He is known to have wanted to avoid a messy court battle over the division of his wealth between his three children by Ms Lario and his two by his first wife, Carla Dall'Oglio.

However lawyers for Ms Lario said she regarded him as the guilty party, and had applied for a formal separation, the first step in divorce proceedings, accusing her husband of being to blame for the breakdown of the marriage.