* Seven managers, former MPs arrested in bid-rigging investigation
* Questions raised over Italy's ability to combat corruption
* PM Renzi attempting to inject confidence into political system
MILAN, May 9 (Reuters) - The arrest of seven managers and ex-members of parliament over alleged attempts to influence public tenders for Milan's Expo 2015 has cast a shadow over Italy's plans to stage an international showcase event and help kick-start the economy.
Italian commentators said the scandal surrounding the Universal Exposition, which has been in the planning and construction stages for more than six years and is expected to draw millions of visitors next year, was another example of Italy's inability to keep corruption out of major events.
It also risks damaging Prime Minister Matteo Renzi's attempts to inject confidence into the political system and counter anti-party populism in Italy ahead of European Parliament elections later this month.
La Stampa newspaper's headline on Friday read: "Bribesville is back", a reference to scandals that brought down Rome's post-war political order in the early 1990s.
"No one should be surprised. The same things that happened before were happening again," Corriere della Sera newspaper said in an editorial.
Those arrested on Thursday included Angelo Paris, the Expo's procurement manager; Primo Greganti, a former senior official in the now-defunct Communist party; and Antonio Rognoni, a former manager of an infrastructure company owned by the Lombardy regional government, the prosecutor in charge of the investigation told a news conference
Two former lawmakers who were once members of former Prime Minister Silvio Berlusconi's party were also arrested.
Greganti was convicted of illicit financing of political parties in 1993 during the so-called 'Clean Hands' operation led by Milan magistrates attempting to uproot systemic corruption.
"There is nothing new under the sun," Antonio Di Pietro, a magistrate turned politician who led the anti-bribery investigations in the 1990s, told La Repubblica daily.
"Corruption continues to exist, today like back then, and nothing has been done to introduce transparency in the public administration," he said.
The arrests took place during a visit by U.N. Secretary-General Ban Ki-moon meant to mark the start of Expo's partnership with the United Nations.
The 600-page arrest warrant, seen by Reuters, exposes widespread corruption and bid-rigging. Prosecutors say those arrested were part of a "criminal ring aimed at influencing procurement" by promising career advancement to public officials through political protection.
Expo 2015 Chief Executive Stefano Sala is meeting Renzi on Tuesday to discuss the economic and political repercussions of the investigation.
More than 140 countries, from Saudi Arabia to the Vatican, will have pavilions at the Expo.
Italy hopes the event, to run from May to October next year, will generate billions of euros in revenue and create thousands of jobs in Italy's financial capital. (Additional reporting by Lisa Jucca; writing by Philip Pullella; Editing by Janet Lawrence)