Electoral authority INE ruled that Morena and its allies secured 364 lower house seats, comfortably exceeding the two-thirds majority of 334 votes needed to amend the constitution without consensus with the opposition.

In the Senate, the ruling party will control 83 of the 128 seats, just shy of the two-thirds majority of 85 seats.

"The decision of INE's general council respects the will of the people," Morena party leader Mario Delgado said on X, pledging to continue the so-called Fourth Transformation political project launched under the current president.

The formal ratification of the June 2 election results comes after opposition parties complained that the ruling coalition should have fewer seats.

Those objections were based on an interpretation of the electoral system prioritizing representation by party rather than coalition.

"The INE neither gives nor takes away congressional or senatorial seats," INE's presiding counselor Guadalupe Taddei said during the marathon seven-hour debate. "Only the citizens can do this with their vote."

Taddei added that the body's actions reflect "our commitment to democracy and the popular will expressed at the ballot box."

The Morena party intends to approve the first part of a series of constitutional changes proposed by outgoing President Andres Manuel Lopez Obrador for the period starting Sept. 1.

These include a controversial reform of the judiciary that would allow judges and magistrates to be elected by popular vote, a move that has rattled markets.

Other amendments aim to abolish autonomous bodies and reform the electoral referee so that its counselors are elected by popular vote and plurinominal deputies are eliminated.

These changes are expected before Oct. 1, when Claudia Sheinbaum assumes her role as the first female president in Mexico's history.