Fresh corruption allegations hit the president of Brazil’s Senate on Monday, with prosecutors linking him to a mega-scandal over the state oil firm Petrobras.

They are the latest in a series of accusations threatening to destabilise the country’s President Michel Temer as he seeks to fix Latin America’s biggest economy.

Senate speaker Renan Calheiros, 61, Brazil’s third-most-powerful official, already faces trial on embezzlement charges in a case that nearly saw him suspended from his post last week.

In a new case, state prosecutors said Monday that they suspect him and another lawmaker of receiving bribes worth some $242,000 from the construction firm Serveng in return for helping it win contracts.

The prosecutors suspect Serveng made donations to the ruling PMDB party that ended up going into Calheiros’s pocket, they said in a statement.

Calheiros denied the allegation in his own statement.

He is considered Temer’s most powerful ally. Together they led impeachment procedures that ended in the removal of Temer’s predecessor, Dilma Rousseff, from office in August.

The Supreme Court this month ordered Calheiros to face trial on separate embezzlement charges.

He has denied accusations in that case that he used public money to make child support payments to a woman with whom he had a baby.

Temer himself was forced on Saturday to deny allegations implicating him in the Petrobras scandal.

He denied asking the construction firm Odebrecht for nearly $3 million in campaign funds for a party candidate, as suspects reportedly told investigators.

Current and former executives of the company have signed plea deals and agreed to cooperate with prosecutors in return for lighter sentences.

The Petrobras scandal has implicated numerous top politicians.

Prosecutors believe a network of executives, politicians and contractors such as Odebrecht systematically plundered the state oil company.