* Former PM charged with "losing" classified reports
* Government has said reports were on corruption, crime
* Winning back EU's trust depends on restoring rule of law
SOFIA, July 14 (Reuters) - Bulgarian prosecutors on Wednesday charged opposition leader and former Prime Minister Sergei Stanishev with mishandling seven classified reports that went missing during his term in power.
Stanishev, who headed the previous government from 2005-09, is now leader of the main opposition Socialist party and called the charges politically motivated. He is the first former prime minister investigated over wrongdoing since the collapse of communism in the Balkan country 20 years ago.
Prime Minister Boiko Borisov has said the missing documents contained details about crime and corruption in the country, which is under pressure to show it can impose the rule of law after years of gaining a reputation for a culture of impunity.
"The Sofia City Prosecutors' Office has raised charges against Sergei Stanishev because ... he has lost seven documents," the prosecutors said in a statement.
"Three of the documents were prepared by the National Security Agency, two by the interior ministry, one by the defence ministry and one by NATO."
Prosecutors have declined to say what they believe happened to the missing documents or give any more details about their contents, which they say are state secrets.
Stanishev has consistently denied wrongdoing.
"There is no doubt that both the investigation office and the prosecutors' office work under enormous pressure from the executive power. They are carrying out a political order by it," news agency FOCUS quoted him as saying.
Borisov said last October that at least nine classified reports on crime, corruption, smuggling and Russia's growing energy influence had disappeared from the government's office during Stanishev's term.
"NEED TO SEE JUSTICE"
Kiril Avramov, an analyst at Political Capital think-tank said the charges against Stanishev were probably not enough to give a big boost to his successor's waning popularity at a time of economic hardship in the European Union's poorest member.
"If Stanishev had been charged with something more substantial, like influence trading or corruption, then we could speak of satisfying people's need to see justice," Avramov said. "Until Borisov does something for the people's incomes, such operations will only have a limited impact."
In November, prosecutors asked parliament to strip Stanishev of his immunity from prosecution and investigate him over the missing reports.
Bulgaria's centre-right government is under pressure to show tangible results in fighting organised crime and graft before the European Union assesses Sofia's progress this month.
A failure to assure the European Union's executive that it can restore rule of law could threaten the country's access to some of 11 billion euros ($14 billion) in EU aid.
Stanishev faces up to two years in prison if found guilty, though prosecutors said the sentence could also be just a fine.
Borisov's government has stepped up its efforts to put an end to a climate of impunity, with prosecutors investigating several ministers for abuse of power and misuse of funds.
Police have arrested scores of suspected kidnappers, smugglers, car thieves and tax fraud schemers in the year since Borisov came to power, but a deepening recession and delayed reforms have eaten away at his popularity.
(Additional reporting by Irina Ivanova; Editing by Peter Graff)
Our Standards: The Thomson Reuters Trust Principles.
