Opposition politicians have launched impeachment proceedings against Chile’s president, Sebastián Piñera, over possible irregularities in the sale of a mining company, after new details about the deal were revealed in the Pandora papers. Lawmakers cited an “ethical duty” to hold the president accountable for the alleged irregularities in his involvement in the controversial Dominga project. Earlier this month Chile’s public prosecutor’s office said that it would open an investigation into possible bribery-related corruption charges and tax violations linked to the sale, which was completed in the British Virgin Islands. The move is the latest blow for centre-right Piñera as he approaches the end of a turbulent four-year term. Presidential and legislative elections are due in November, with polls suggesting leftwing candidates are likely to gain ground. The Pandora papers – the biggest trove of leaked offshore data in history – revealed new details of the controversial mining deal. Piñera’s family sold their stake in the Dominga mine project in 2010 to his close friend and business partner, Carlos Alberto Délano. The Pandora papers investigation found evidence to suggest that the third installment of the payment contained a clause requiring the government not to strengthen environmental protections in the proposed area for the mine in the north of Chile. Jaime Naranjo, a leftist lower house lawmaker and one of the drivers of the impeachment proceeding, said Piñera had “openly infringed the constitution … seriously compromising the honor of the nation”. Piñera, whose fortune amounts to $2.5bn according to Forbes magazine, has rejected the accusations and argued that no irregularities had been found in the deal. Amid the scrutiny of his business affairs, Piñera on Monday announced a state of emergency in four provinces in the south of the country where tensions have run high between the Mapuche people, Chile’s largest indigenous group, and police and powerful landowners. Unrest has shaken the region since the 2018 killing by police of an unarmed Mapuche man – and the ensuing cover-up – sparked angry protests throughout the country. The new measures will restrict movement and the right to assembly in the wake of recent arson attacks, as well as increase military and police presence in the area further still. Indigenous activists have questioned the timing and purpose of the measure, announced on the anniversary of Christopher Columbus’s arrival in the Americas. They say that the state of emergency, which will last for 15 days but can be extended to 30, has been enacted to cynically divert attention away from investigations into the president. Piñera is also still under pressure over the brutal repression of anti-inequality protests in 2019 and 2020. His former interior minster, Andrés Chadwick, was impeached by congress at the height of the protests in December 2019, and Piñera himself narrowly avoided impeachment in a similar vote a few days later. In April, Baltasar Garzón – the Spanish judge who worked to hold the dictator Gen Augusto Pinochet accountable for crimes committed during his 1973-1990 regime – filed an accusation at the international criminal court in The Hague alleging Piñera’s complicity in alleged human rights crimes during the unrest. The president has denied any wrongdoing. The latest motion to impeach the president could be voted on in congress before the first round of Chile’s general election on 21 November. If approved by the lower house, it moves up to the senate, where it must be approved by a two-thirds majority if Piñera is to be removed from office.