Opponents of Peru's President Pedro Pablo Kuczynski are calling on him to resign over payments he received a decade ago from a Brazilian construction company at the center of Latin America's biggest graft scandal.

Lawmakers from the nation's two biggest parties said Thursday they would initiate impeachment proceedings against Kuczynski unless he resigns.

The threat comes a day after evidence emerged that as a Cabinet minister in a previous government Kuczynski's consulting business received payments of $782,000 from consortiums led by Odebrecht.

Kuczysnki said he's done nothing wrong but his failure to explain the payments and past denials that he had any ties to Odebrecht have earned widespread rebuke even from supporters.

As the political crisis deepened, Peru's stock exchange on Thursday had its biggest tumble in two years.