File photo of Eduardo Cunha (AFP).
Brazil's political turmoil deepened Friday when the speaker of the lower house of Congress, a key figure in President Dilma Rousseff's fragile ruling coalition, announced he was joining the opposition.
The announcement by Eduardo Cunha, a leader of the centrist PMDB and the lower house's powerful speaker, formalized an increasingly bitter personal split with Rousseff, whom he has also threatened to impeach.
"From today, the speaker of parliament is in opposition," he said live on national television in the capital Brasilia.
Cunha said "I will ask my party to go into opposition."
The PMDB, a longstanding coalition partner with Rousseff's leftist Workers' Party, issued a cautious statement that left open the question over whether it will heed Cunha's call.
Cunha "expressed a personal position, which we respect," the party said in a statement.
But it also noted that any decisions had to be taken by relevant commissions according to party rules.
Rousseff did not react publicly and her office said only that the PMDB "played and continues to play an important role in the heart of the government."
The latest salvo in Cunha's battle with Rousseff follows the allegation Thursday that the speaker demanded a $5 million bribe as part of the sprawling bribes-and-kickbacks scheme centered on national oil company Petrobras.
Cunha blasted the allegation as politically motivated.
The Petrobras scandal, looming recession and an inability to connect with voters in the same way as her Workers' Party predecessor Luiz Inacio Lula da Silva have left Rousseff reeling since the start of her second term last year.
Now Cunha is threatening to up the ante.
As speaker, he has the authority to initiate impeachment proceedings that some opponents in Congress want over what they say was illegal campaign financing. He says he will take a decision within 30 days.
In a televised press conference, Cunha said there was "a band of nutcases" in the government who "have hatred toward me."
Although she did not respond directly to her latest troubles, she said at a summit of regional leaders: "There is no space for anti-democratic adventures in South America."
Recently, Rousseff has repeatedly alluded to Brazil's recent history of military dictatorship, accusing her own opponents of seeking to mount a "coup."