By James Mackenzie

ROME (Reuters) - Italians' suspicion of their politicians is rarely far from the surface, and a spate of scandals has further hurt the credibility of the main parties just before their first voter test since the downfall of Silvio Berlusconi.

Local elections on Sunday and Monday look set to confirm a growing pattern of disillusion. They will provide the first test for the increasingly unpopular austerity measures of technocrat Prime Minister Mario Monti since he took over in November, and will set the tone ahead of national elections next year.

More than 8 million voters - or about 13 percent of the population - are eligible to vote in some 800 municipalities including Palermo and Verona, and the mood appears increasingly hostile both to Monti and the parties that back him in parliament.

The protest vote is expected to be significant, analysts said, and some predict a low turnout. A survey last week showed 48 percent of voters either undecided or ready to abstain.

The election of mayors and city councilors will have no direct impact on Monti's ability to press on with the structural reforms he has promised to revive a stagnant economy and control a towering public debt.

But the fractious climate has alarmed many politicians, and fueled the headline-grabbing campaign of Beppe Grillo, a maverick comedian whose movement is contesting several races.

"There is great mistrust and disregard for politics in Italy, there's no doubt about that," said former Foreign Minister Franco Frattini, a prominent moderate in Berlusconi's centre-right PDL party, which supports Monti in parliament alongside the centre-left PD.

"Unfortunately, that's opened up space for these very dangerous populist phenomena like Grillo. Not just in Italy but in many other countries in Europe as well," he told Reuters.

Several candidates are running under local independent lists, and a survey by pollster Demopolis last week put trust in the big parties at just 5 percent.

SUFFERING

Main political parties appear to have done little in recent weeks to regain the lost ground.

While Berlusconi has mostly kept a low profile since being forced out, his PDL party, Italy's largest, is reeling from the former prime minister's perceived mishandling of the economic crisis and looking for a new direction after two scandal-filled decades.

Berlusconi's old allies in the Northern League, who rose to prominence on a pledge to fight corrupt politicians in Rome, are now embroiled in accusations that party leaders used taxpayers' money for luxury cars, holidays and home repairs .

League founder Umberto Bossi has denied the allegations but has been forced to step down. A separate scandal engulfed the former treasurer of a now-defunct party whose officials eventually came to be part of the PD.

The League and the PDL are running separately this time. The center-left stands to gain, with the PD having held a steady lead in national opinion polls for months. But whether the chronically fragmented center-left bloc will be capable of a united front in next year's general election remains to be seen.

Italy is stuck in recession, a third of young people are unemployed and data last week showed consumer confidence at its lowest since readings began in 1996, while inflation far outstripped wages which grew at their slowest pace since 1983.

Opinion polls show Monti's approval ratings have come down as taxes have gone up and his promised labor reforms have been interpreted by many as a scheme to let firms fire workers rather than as a path towards more jobs.

(Editing by Alessandra Rizzo)