(Adds comments, background on Petrobras scandal throughout)
By Guillermo Parra-Bernal
SAO PAULO, April 2 (Reuters) - Financial bourse BM&FBovespa SA presented on Thursday a plan to strengthen corporate governance rules for Brazilian state-controlled companies, in response to a corruption scandal engulfing oil producer Petróleo Brasileiro SA.
State firms will adhere to the new framework on a voluntary basis, Chief Executive Officer Edemir Pinto said at an event. The rules will be put to public hearings with a limited number of market participants beginning April 22.
The discussions will focus on enhancing transparency, fine-tuning controls on the boards and auditing committees of state companies, and implementing more transparent methods for selecting management, said BM&FBovespa executive Flavia Mouta.
The framework should be ready by June 30.
"Corporate governance rules that are voluntary in nature help bring about a premium not only for the company and minority shareholders but also for the controlling shareholder, which will be seen as a more trusted entity," Pinto said.
The plan comes as the findings of a corruption probe at Petrobras, as the state-run oil company is known, have bruised confidence in Brazil's governance standards and hurt local and foreign retail investors who invested in Petrobras stock.
Prosecutors allege that Petrobras executives conspired with some of the nation's largest engineering companies to inflate contracts for refineries, ships and other goods and services. Some of the excess sums were kicked back to executives and members of President Dilma Rousseff's ruling coalition as bribes and campaign contributions, according to prosecutors.
Minority investor groups also claim the ruling Workers' Party has used Petrobras, which is controlled by the federal government, and other state companies and pension funds as tools for various policy objectives since coming to power in 2003.
Investors such as Franklin Templeton Investment's Mark Mobius said the government-sponsored, $70.3 billion capitalization of Petrobras in 2010 failed to respect the rights of minority investors.
Brazil's securities industry watchdog CVM sees the new framework as key to help align the interests of the government and minority shareholders, CVM President Leonardo Pereira said at the event.
This is not the first time that BM&FBovespa has taken steps to protect investors. Previous efforts include the creation of the so-called Novo Mercado, part of the São Paulo stock exchange that established the "one-share, one-vote" rule in 2000. (Reporting by Guillermo Parra-Bernal; Editing by Chizu Nomiyama and W Simon)