Brazil’s tourism minister Henrique Eduardo Alves has stepped down before vote on President Dilma Rousseff’s coalition.
Opposition lawmakers want to remove Dilma Rousseff over claims she manipulated accounts to hide growing deficit.
Officials from Dilma Rousseff’s coalition allies, the Brazilian Democratic Movement Party (PMDB), will vote to leave the alliance on March 29, members said.
Dilma Rousseff, a former political prisoner during Brazil’s military government, began her second term in office 14 months ago.
However, her popularity has plummeted amid corruption allegations around senior members of the governing Workers’ Party.
The speaker of the lower house of Congress, Eduardo Cunha, agreed in December to open impeachment proceedings against her.
Last week, Dilma Rousseff, who denies wrongdoing, said the procedure amounted to a coup. She met officials from the PMDB ahead of that party’s national leadership meeting on March 29.
However, a number of lawmakers from the PMDB said ahead of the meeting that most members had already decided to abandon the coalition.
The PMDB is headed by Michel Temer, Dilma Rousseff’s deputy, who would become president should she be removed.
The loss of support by his party’s 69 lawmakers could have consequences for the impeachment proceedings. Dilma Rousseff needs the support of a third of the 513 members of the lower house of Congress to stave off impeachment.
The Workers’ Party has been in power since former President Luiz Inacio Lula da Silva was sworn in for his first term in 2003.
It has been hit by a long-running investigation into bribes from contractors working for state oil company Petrobras.
A recent attempt by Dilma Rousseff to appoint Luiz Inacio Lula da Silva as her chief of staff was seen by critics as an attempt to shield him from money-laundering charges – which he denies – connected with the case.
His appointment was blocked by a judge earlier this month.
Luiz Inacio Lula da Silva said on March 28 he expected Dilma Rousseff to survive growing pressure, and said he would speak to Michel Temer to work out how to save her job.
Protests involving tens of thousands of people have taken place across Brazil to call for Dilma Rousseff’s impeachment.
According to poll by the Datafolha poll in late February, only 11% of respondents across the country said President Dilma Rousseff’s performance was “good or excellent”.