Leftist President Pedro Castillo, still in his first year in office, has already survived two previous efforts by conservative critics in Congress to remove him from power, amid deepening economic and political turmoil in the Andean nation, the world's second-biggest copper miner.

The latest twist targets Vice President Dina Boluarte, a Castillo ally, for an alleged conflict-of-interest constitutional violation, that if sustained, could lead to her removal and then potentially allow for the president's own suspension.

"They're looking to stage a coup from Congress," said Boluarte lawyer Alberto Otarola, who added that late last month he petitioned the human rights commission of the Washington-based Organization of American States (OAS) to order a suspension of the investigation into the vice president.

The petition to the OAS argues that Boluarte's rights are being undermined by the opposition's charges, Otarola explained.

Like other countries across the region, Peru adheres to rulings from the OAS' rights commission, known as the CIDH, which it views as legally binding.

If Boluarte could be brought down, which would only take a simple majority of the 130-seat Congress, her removal would likely further weaken Castillo, whose popularity ratings have dipped to record lows in recent months.

Deposing Castillo in an impeachment trial would require 87 votes, which analysts see as unlikely.

The charges against Boluarte should be confirmed sometime later this month by a special congressional committee, according to a legislative source, ahead of an expected vote by a full session of congress.

Boluarte is accused of carrying out her duties as a minister at the same time she represents a private civil association, which her accusers say is banned by the constitution.

But Otarola said Boluarte relinquished her private duties before assuming her ministerial responsibilities.

The probe into Boluarte is the latest in a series of blows for Castillo, who last month faced questions from prosecutors investigating separate corruption allegations in a three-hour session.

Castillo, who initially spooked investors with threats to boost state control of the economy, has lately moderated his tone as he confronts upheaval in the key mining sector and beyond. He has maintained his innocence.

(Reporting by Marco Aquino; editing by Jonathan Oatis)

By Marco Aquino