The leader of Italy's centre-left opposition resigned on Tuesday after a regional election defeat to the party of Prime Minister Silvio Berlusconi, who has been consolidating his strength despite a deep recession.

Walter Veltroni confirmed his intention of quitting, a spokesman for his Democratic Party (PD) said, even after party bosses initially ruled out the possibility following their routing in the governor's race on the island of Sardinia.

Analysts said the opposition had failed to capitalise on a grim economic recession, set to become Italy's longest since World War Two, and was weakened by constant internal bickering and a string of corruption scandals.

"The economic crisis has started to bite the country. The paradox is that the responsibility isn't put on the government, but on its rivals," wrote columnist Massimo Franco, in a piece analysing Berlusconi's victory for Corriere della Sera daily.

Berlusconi, a billionaire media mogul with a luxury villa in Sardinia, had criss-crossed the Mediterranean island campaigning for his party to capture a region previously controlled by centre-left rivals.

His party's candidate for Sardinia governor, Ugo Cappellacci, the son of Berlusconi's tax adviser, had 52 percent of the vote by midday on Tuesday and was declared victor.

That compared with 43 percent for rival Renato Soru, the former Sardinia governor and founder of telecoms firm Tiscali. Soru, also the owner of left-leaning newspaper L'Unita', had been tipped as a future leader for the centre-left opposition.

His defeat was the latest blow for Veltroni, who was badly beaten by Berlusconi in a parliamentary election last year. Since then, the opposition has been in disarray, while Berlusconi's government has enjoyed record popularity ratings depsite the economic crisis.

Newspaper Il Giornale, which is owned by Berlusconi's family, called the Sardinia vote a "Coup de Grace" on the centre left, and analysts said the PD appeared to be in a downward spiral and needed a change in course.

"Truly, one can't see where the PD can begin to stem a haemorrhaging of consensus and credibility that looks unstoppable," wrote Federico Geremicca on the front page of La Stampa newspaper.