* Prosecutor says Italy's economy polluted by crime
* Fears success by Monti
* Says war against mafia has failed, must change
By Barry Moody
ROME, Feb 6 (Reuters) - Sicilian prosecutor Antonio Ingroia has left his job fighting the mafia to stand in Italy's election, saying politicians
have totally failed to fight organised crime, corruption and tax evasion that are crippling the economy.
Ingroia, heading the most leftwing force in the campaign, says outgoing Prime Minister Mario Monti is a bigger danger politically than centre-right leader Silvio Berlusconi, who he believes has no chance of winning the Feb. 24-25 poll.
Critics accuse the bearded Ingroia, 53, of being an extremist and say the way in which he left his job little more than a month ago and suddenly jumped into the election campaign raises new questions about the political leanings and lack of impartiality of Italy's magistrates.
But Ingroia rejects suggestions that he is playing into the hands of Berlusconi, who has accused leftist magistrates for decades of waging a political war against him with the launching of around 30 prosecutions, including a current case in which he is accused of paying an underage prostitute.
"We would be playing Berlusconi's game if we didn't do something like this. To be subordinate to his lies and media tricks would mean letting him win," Ingroia told Reuters in an interview at a cafe outside his Rome hotel, as burly police bodyguards watched the street.
Ingroia has been subjected to constant threats since he entered the anti-mafia pool of legendary prosecutors Giovanni Falcone and Paolo Borsellino in 1987. Both of his mentors were murdered in huge bomb explosions in 1992.
His Civil Revolution group includes another prosecutor who turned to politics, Antonio Di Pietro, who became famous for the "Bribesville" cases in the early 1990s that swept away Italy's postwar political order and paved the way for Berlusconi.
Ingroia said that while Berlusconi was the principle adversary of the left, "after 20 years Italians are now fortunately vaccinated against him."
Monti was more dangerous because of an increasing chance that centre-left Democratic Party leader Pier Luigi Bersani may seek an alliance with him in order to rule after falling short of an adequate majority in the election.
"I cannot hide my esteem and respect for Monti as a competent person who is serious and understands the economy...but it is exactly for this reason that, being more authoritative in the eyes of public opinion, he is more dangerous," Ingroia said.
Such an alliance with Monti, who Ingroia said had promoted the power of banks and big business, would betray progressive voters who wanted a centre-left government but would end up with a neo-liberal one following policies closer to Berlusconi.
"It is better that Democratic Party voters know this before they vote," said Ingroia, who joined the campaign in December after returning to Italy from a temporary United Nations job working with anti-narcotics investigators in Guatemala.
Ingroia called on Bersani to ally instead with his new leftist grouping, which is currently polling around 5 percent, enough to enter the lower house but not the Senate.
Asked why he had entered politics rather than continuing the legal battle against crime, Ingroia replied: "The question of morality, of corruption, of collusion with the mafia is central...Up to now traditional politicians have not done what is necessary despite repeated appeals."
BEATING THE MAFIA
Defeating Cosa Nostra was a political issue and could not be left only to judges and the police. Italy had for centuries assumed that the mafia could not be eliminated, he said.
"We need a new policy not of containment but of annihilation. This must be directed by the government and parliament."
He added: "We must hit the mafia at its heart which is above all financial...a good part of Italy's economy is based on illegality, from organised crime, corruption and major tax evasion. We must hit all these three legs of the illegal economy which pollutes Italy's economy."
He said Italy's Byzantine justice system, which is crippled by a massive backlog of cases and years of delays, must be comprehensively reformed.
The system was the result of irresponsible past policies and moves by Berlusconi and his friends to gain impunity. "The result is no citizen can have faith in justice, no entrepreneur, no foreign investor has the courage and belief to invest in Italy."
In his 25-year career, Ingroia has frequently led cases involving alleged links between the mafia and politicians and businessmen, including a close associate of Berlusconi.
Ingroia was also involved in a case in which President Giorgio Napolitano won a ruling by Italy's top court to destroy wire taps of a conversations between him and a former interior minister, who could face trial for alleged secret negotiations between Cosa Nostra and state officials 20 years ago.
Ingroia says the negotiations led to the killing of Borsellino, who opposed talking to gangsters who wanted concessions in exchange for ending a spate of assassinations and bombings against state targets that killed 21 people. (Writing by Barry Moody; Editing by Jon Boyle)