Brazilian President Dilma Rousseff's shaky political standing suffered a new blow Friday when one of the most powerful leaders of a party in her ruling coalition declared he was heading into the opposition.

The announcement by Eduardo Cunha, a leader of the centrist PMDB and speaker of the lower house of parliament, 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 wider effect on PMDB's longstanding coalition with Rousseff's leftist Workers' Party was not immediately clear.

However, the influential Cunha's declaration of war heralded new worries for the already deeply unpopular Rousseff.

Corruption scandals, 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.

But Cunha, who says he may soon seek to initiate impeachment proceedings against Rousseff, has his own problems.

Late Thursday, the powerful speaker was accused by a jailed former consultant of having demanded a $5 million bribe as part of the sprawling bribes-and-kickbacks scheme centered on national oil company Petrobras.

Cunha denies the accusations.