Mexican President Andres Manuel Lopez Obrador said Wednesday that his predecessors Enrique Pena Nieto and Felipe Calderon should testify about corruption allegations linked to a scandal-tainted Brazilian construction giant.

The call follows accusations made by Pena Nieto's former advisor Emilio Lozoya that multi-million-dollar bribes from Brazil's Odebrecht had financed the presidential campaign that brought him to power in 2012.

"Ex-president Calderon and ex-president Pena (Nieto) have to testify," Lopez Obrador said at his daily news conference, calling on Lozoya to present evidence to support his claims.

Other politicians should also be held to account, the leftist leader said, while adding that he respected the independence of prosecutors.

Lozoya, Pena Nieto's chief international strategist prior to the 2012 election, was extradited from Spain last month to stand trial on corruption charges linked to Odebrecht, Latin America's biggest construction company.

The 45-year-old, who went on to head state oil giant PEMEX from 2012 to 2016 during the Pena Nieto administration, has been given the status of cooperating witness.

Lozoya has admitted that bribes of around $4.4 million from Odebrecht "were mainly used for the 2012 presidential campaign," Attorney General Alejandro Gertz told reporters on Tuesday.

Lozoya alleges that Pena Nieto and his campaign coordinator Luis Videgaray "were the ones who ordered that this money be delivered to various foreign electoral advisors," Gertz added.

Lozoya also accused Pena Nieto and Videgaray, who was then finance minister, of buying votes for structural reforms in 2013 and 2014, including the opening up of the energy sector after 75 years of state monopoly.

He linked Calderon, who was in office from 2006 to 2012, to alleged irregularities in Odebrecht's construction of a petrochemical plant in Mexico.

Lozoya is accused of accepting bribes worth more than $10 million from Odebrecht, which has admitted to handing out hundreds of millions of dollars to win contracts in 12 countries.

The scandal has toppled former presidents and high-ranking officials in several countries including Brazil, Peru and Colombia.