Berlusconi has been a staunch supporter of Bush's war in Iraq
The White House has apologised to Italian PM Silvio Berlusconi for a briefing describing him as a political "amateur" who is "hated by many".
The "insulting" biography was included in a press kit distributed to reporters travelling with President George W Bush to a meeting of world leaders in Japan.
He was "one of the most controversial leaders" of a country "known for governmental corruption and vice".
Only last month, Mr Bush visited his old ally, calling him a "good friend".
The four-page description of Mr Berlusconi had been taken from the Encyclopedia of World Biography.
It refers to the Italian prime minister as a man "hated by many but respected by all at least for his bella figura (personal style) and the sheer force of his will".
It says Mr Berlusconi was said to be "regarded by many as a political dilettante (amateur) who gained his high office only through use of his considerable influence on the national media".
Acknowledging the error, White House spokesman Tony Fratto issued an apology.
"A biography of Italian Prime Minister Berlusconi included in the press package used language that is insulting both to Prime Minister Berlusconi and to the Italian people," Mr Fratto said in a statement.
"We apologise to Italy and to the prime minister for this very unfortunate mistake.
"The sentiments expressed in the biography do not represent the views of President Bush, the American government, or the American people," he said.
Mr Berlusconi was a key supporter of the US-led war in Iraq.
During Mr Bush's farewell tour of Europe last month, Mr Berlusconi called the US leader "a personal friend of mine and also a great friend of Italy".
To which Mr Bush responded: "You're right. We're good friends."