A Brazilian senator charged with trying to obstruct a major corruption investigation has accused Education Minister Aloizio Mercadante of offering him money in exchange for his silence.
Senator Delcidio Amaral has made the accusations as part of a plea bargain with the chief prosecutor's office.
He has said he will reveal details of the corruption scheme at the state oil company, Petrobras, in order to get a more lenient sentence.
Mr Mercadante denies the allegations.
"I never tried to stop him from signing a plea bargain. That is a right he has," said Mr Mercadante, who rejected calls for his resignation.
In Senator Amaral's testimony to prosecutors, he says Mr Mercadante offered financial assistance in order to divert him from the idea of collaborating with the prosecution.
President Dilma Rousseff has also denied involvement, issuing a statement "vigorously rejecting" what she described as "a personal initiative" by Mr Mercadante.
She was angered by his decision to approach Senator Amaral's top aide and demanded an explanation from the minister, O Globo newspaper reported.
Mr Amaral is the government's former leader in the upper house of Congress.
Prosecutors have accused senior members of the governing Workers' Party, including former President Luiz Inacio Lula da Silva, of involvement in the Petrobras scandal.
Lula is expected to meet Ms Rousseff later on Tuesday to discuss the possibility of taking a post in cabinet.
This is the latest development in the political crisis around Ms Rousseff's government.
Members of the Workers' Party say Lula's appointment would strengthen her beleaguered government.
As a government minister, the former president would escape the jurisdiction of Federal Judge Sergio Moro, who is seen as hostile to the Workers' Party.
His case would be heard by the Supreme Court instead.
Senator Amaral was arrested in November, accused of plotting to smuggle a convicted former executive of Petrobras, Nestor Cervero, out of the country.
Mr Amaral became the first sitting senator arrested in Brazilian history.
A Supreme Court judge ordered his release last month and authorised him to go back to his normal activities in the Senate.
Brazilian media speculated at the time that his release was conditional to him agreeing to testify against other suspects in the Petrobras scandal.
One of Brazil's richest men, banker Andre Esteves, was arrested as part of the same operation.
Mr Esteves, Brazil's 13th richest man, worth an estimated $2.5bn (£1.7bn), also denies the charges against him.
The Petrobras scandal has damaged the popularity of President Rousseff, who was sworn in to a second four-year term in January 2015.
Ms Rousseff is not implicated in the corruption scheme, but she was head of Petrobras during the years when much of the alleged corruption is believed to have taken place.
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