Brazilian police have arrested a close ally of the country’s embattled president Michel Temer, just as he seemed to be marshalling forces to fight a corruption crisis that has shaken his administration to its foundations.

Geddel Vieira Lima, a former cabinet minister who resigned in November, was detained in the north-eastern state of Bahia in a police operation investigating irregularities at a government-controlled bank.

The arrest came a week after Brazil’s prosecutor-general charged Temer and an aide and former lawmaker with corruption. The president has angrily denied the accusations, and vowed to continue an unpopular programme of austerity measures.

“It is a scenario that worsens Temer’s situation because Geddel Vieira Lima was one of the principle articulators of the Temer government,” said Maurício Santoro, a professor of international relations and political scientist at the State University of Rio de Janeiro. “The last weeks have been a rollercoaster for Temer.”

This week, Brazil’s congress is to begin discussing the corruption charges. If two-thirds of the lower house vote in favour, Temer will be suspended from office for 180 days and tried by the supreme court.

Prosecutors said in a statement that Lima and Eduardo Cunha – the former speaker of Brazil’s lower house who has been jailed since last year – acted to free up loans from the government-controlled Caixa Econômica Federal. Lima formerly served as one of the bank’s vice-presidents. Prosecutors said he was trying to obstruct the investigation.

Some of the companies that benefited from the deals were controlled by J&F Investimentos, a holding company that also controls the country’s biggest meat-packing firm, JBS, which has played a central role in corruption allegations against the president.

Temer’s latest political crisis began in May when Joesley Batista, an heir to the JBS empire, secretly recorded a conversation with the president in an unofficial late-night meeting, prior to cutting a generous plea bargain deal with prosecutors.

During the conversation, Temer appeared to endorse Batista obstructing the investigation and making payments to Cunha.

Temer’s presidency has been bogged down in a string of graft scandals since he took over from the leftist Dilma Rousseff, whose vice-president he was, in a controversial impeachment process.

“He is threatened on so many sides, there are so many threats, that it is impossible for him to deal with so many situations,” said Santoro. “There will always be one he can’t resolve.”