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The firebrand founder of a populist, Italian anti-immigrant party, whose crucial support kept Silvio Berlusconi in power in three governments, resigned Thursday amid a widening corruption scandal over party funds.

Umberto Bossi tendered his resignation as Northern League secretary, the top post, at a summit of party officials in Milan and repeatedly rebuffed pleas by his colleagues to change his mind, said a League statement.

In a show of support for Bossi, 70, who made a stunning comeback after a 2004 stroke left him barely able to speak, party officials made him League president and also asked him "to carry on with his political activity with even greater determination and conviction," the party said.

Until a new secretary is chosen, the League will be led by a triumvirate of officials, including Roberto Maroni, the party's No. 2, who served as interior minister under Berlusconi.

League official Matteo Salvini, speaking on Radio Padania, the League's broadcaster, quoted Bossi as saying that wrongdoers in a scandal involving alleged skimming of party funds should "pay" for their errors. Bossi himself has denied wrongdoing, but corruption prosecutors have been probing the activities of his family, including his son, Renzo, a rising star in the party.

Thursday's League meeting also saw the naming of an official to replace the party's treasurer, Francesco Belsito, who resigned earlier in the scandal. In a bid to remove corruption suspicions overshadowing the party, League officials have decided to immediately submit the party's ledgers and assets to review by independent accountants.

Bossi's decades-long support made him Berlusconi's lynchpin coalition partner in three governments led by the media mogul. When Bossi abruptly yanked his backing in late 1994, Berlusconi's first government collapsed.

Berlusconi resigned as premier in November amid Italy's worsening financial crisis, and was replaced by economist Mario Monti, who was tasked with saving the country from a eurozone debt crisis. The billionaire business mogul has been coy about whether he will run again after parliament's term runs out in spring 2013, when the non-elected Monti has said he will leave office. Berlusconi has tapped his former justice minister, Angelino Alfano, as secretary of his own Freedom People party and political heir.

Berlusconi himself has spent most of his political career fighting corruption probes and is currently on trial in Milan on charges of having had sex with a Moroccan prostitute when she was 17 and underage, and then trying to use his office to cover it up. He denies wrongdoing.

The scandal involving alleged embezzlement of League funds shames Bossi's justification for creating the party as a regional bulwark in the affluent north against what he denounced as corrupt and tax-wasting Rome-based parties.

Bossi originally pushed for the north to secede from the lagging south, but later softened his goal to federalism for a country heavily controlled by Rome. The maverick whipped up a largely local, folksy movement called the Lombard League into the Northern League, the main coalition partner in all of Berlusconi's governments.

The combination of the smooth-talking, impeccably dressed billionaire and Bossi, an often vulgar-speaking, ill-dressed homebody, made for the oddest of political couples. Essentially acknowledging his political debt to Bossi, Berlusconi made crackdowns on immigrants a plank of his government.