(Add comments by Calheiros and Jucá, political context)
By Silvio Cascione
BRASILIA, June 7 (Reuters) - Brazil's top prosecutor is seeking the arrests of the Senate leader and other senior ruling party politicians for allegedly trying to obstruct a corruption probe, threatening to undermine President Michel Temer's interim government, O Globo reported on Tuesday.
Those targeted are Senate President Renan Calheiros, Senator Romero Jucá, the president of the ruling PMDB, former Brazilian President José Sarney and the suspended speaker of the lower house of Congress, Eduardo Cunha, the newspaper said.
Prosecutor General Rodrigo Janot accuses them of seeking to block a sprawling two-year-old investigation into political kickbacks on contracts with state-run oil company Petrobras , according to the report.
The four men, powerful members of Brazil's political establishment and the centrist PMDB, the country's largest party, have denied the accusations.
The Supreme Court must authorize their arrests.
Their arrests would be a severe blow to Temer, who is struggling to establish his government's legitimacy less than a month after he replaced now suspended leftist President Dilma Rousseff.
A string of recent scandals has weakened the interim president as he seeks to build support in the Senate to convict and definitively remove Rousseff for breaking budget laws. Rousseff has described her suspension and possible removal from office as a coup.
The obstruction of justice obstruction against the PMDB figures should add weight to Rousseff's argument that corrupt politicians conspired to remove her from office to stop prosecutors from taking action against them.
Jucá, who briefly was Temer's planning minister, and the interim president's first pick for anti-corruption minister were forced to step down after leaked recordings stoked accusations they were conspiring to stymie the Petrobras probe.
Their departures, along with policy reversals and second-guessing in Temer's Cabinet, have added to concerns that the political crisis will continue to simmer for months, paralyzing policy amid the nation's worst recession in decades.
Brazil's benchmark Bovespa stock index has fallen 5 percent since Temer took office.
Calheiros and Jucá issued public statements on Tuesday denying they obstructed the Petrobras investigation. Calheiros called the request for his arrest "unreasonable, disproportionate and abusive." Juca and Cunha called it "absurd."
The chief prosecutor also requested that Calheiros be removed from the Senate presidency, O Globo said. If suspended, Calheiros would be replaced by Senator Jorge Viana, a Rousseff ally, adding a new wrinkle to Rousseff's impeachment battle.
Rousseff's trial is expected to conclude in mid-August as Brazil is hosting the Olympic Games in Rio de Janeiro.
Under Brazilian law, the Supreme Court must approve any judicial action taken against members of Congress. Sarney was included in the request, even though he is no longer a senator, because he is mentioned in the same case as Jucá and Calheiros.
The chief prosecutor's request to the Supreme Court followed the release of recordings made by Sergio Machado, a former senator and PMDB ally who struck a plea bargain deal with prosecutors to cooperate in the sweeping corruption probe that has plunged Brazil into political mayhem.
Machado recorded Calheiros, Jucá and Sarney, separately, allegedly discussing strategies to weaken the investigation.
The recordings were leaked by newspapers in recent weeks and caused Jucá's dismissal as planning minister.
Machado, a former president of the oil transportation unit of Petrobras, said in his plea bargain statement that he gave Calheiros, Sarney and Jucá 70 million reais ($20 million) in graft money, O Globo reported on Friday.
The Supreme Court voted unanimously last month to remove Cunha, a bitter rival of Rousseff, as speaker of the lower house on charges of abusing his power to obstruct an investigation by the chamber's ethics committee.
The committee met on Tuesday to decide whether to strip Cunha of his seat and ban him from running for office for eight years for lying to the lower house about undeclared Swiss bank accounts. Cunha is under investigation for receiving kickbacks on Petrobras contracts and hiding $16 million in Switzerland.
A press representative for Sarney did not immediately respond to requests for comment. Spokeswomen for Janot and the Supreme Court declined to comment.
$1 = 3.46 Brazilian reais Additional reporting by Anthony Boadle and Pedro Fonseca; Editing by W Simon, Daniel Flynn and Paul Simao