BRASILIA (Reuters) - Brazil’s attorney general urged a congressional committee on Monday to dismiss impeachment charges against President Dilma Rousseff, saying there is no legal basis for the proceedings.

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Jose Eduardo Cardozo, the government’s main legal advisor, told members of Congress that the decision by lower house speaker Eduardo Cunha to accept the impeachment request was motivated by Cunha’s desire for political revenge against Rousseff, his bitter political rival.

“The impeachment process was compromised from the start and as such it is invalid,” Cardozo said, telling lawmakers that to conclude the impeachment would be to “rip up the constitution.”

The hearing came just weeks ahead of a vote that could suspend Rousseff from office in the middle of an economic crisis and a bribery scandal at state-run oil company Petrobras that has shaken Brazil’s political establishment. Markets favor Rousseff’s ouster on hopes it could usher in business-friendly policies under her substitute, Vice President Michel Temer.

The opposition’s impeachment request, which is not formally tied to the graft probe threatening her inner circle, alleges that Rousseff deliberately manipulated budgetary accounts to boost her re-election campaign in 2014.

Cardozo, Rousseff’s former justice minister, denied allegations that lending from state banks to the federal government was used to fund social programs. The testimony by the attorney general, appointed in March, is the latest step in a process that started with Cunha’s acceptance of impeachment charges in December.

The committee will recommend to the lower house whether there are grounds to impeach Rousseff. The full house would then vote on the committee’s decision, which could happen as soon as mid-April.

If the impeachment passes the lower house, Rousseff would be suspended for up to six months while facing trial in the Senate, making Temer acting president. Temer and Cunha’s PMDB party, the largest in Congress, formally broke with the government last week.

Rousseff’s opponents need the votes of two-thirds of 513 deputies to take the impeachment case to the Senate. Rousseff has to get 171 votes or abstentions to block the process. Political consultancies, such as the Eurasia Group, see a 60-70 percent chance she will lose the vote.

In an effort to rally her leftist base and consolidate support to defeat impeachment, Rousseff last month appointed her predecessor and political mentor, former President Luiz Inacio Lula da Silva, as cabinet chief.

The move set off a wave of legal challenges from critics accusing her of shielding Lula from the snowballing corruption investigation that started at state-run oil company Petroleo Brasileiro SA, known as Petrobras.

Prosecutors have charged Lula with concealing a luxury beachfront apartment provided by Petrobras contractors snared in the multi-billion-dollar graft probe.

If Lula takes office as Rousseff’s minister, proceedings against him will remain under the jurisdiction of the Supreme Court.

A dozen other impeachment requests are also waiting for consideration by Cunha, a fierce critic of Rousseff who himself is facing corruption charges for allegedly receiving millions in the Petrobras scheme through undeclared Swiss bank accounts.

Cunha can accept a second bid to impeach the president in tandem with the current process but he is expected to do so only if the first case against Rousseff is defeated.