Mexico's Congress has approved an anti-corruption law that could help relieve pressure on President Enrique Peña Nieto's scandal-plagued government.

The law, passed late on Tuesday night, strengthens oversight of public officials and designates a special prosecutor to tackle corruption. It comes after several previous efforts to pass anti-graft measures failed.

The reform will give new powers to Mexico's existing Federal Audit Office and the Public Administration Ministry (SFP), as well as creating a special court to oversee all corruption-related issues.

Details of the changes will be hashed out in secondary laws that must be passed in the next year.

Opposition parties joined with Peña Nieto's party to approve the law, but some anti-corruption organizations have expressed concern that the project will just give a face lift to existing institutions and will not address the low rate of prosecutions for corruption in Mexico.

Peña Nieto's focus on reforming Mexico's struggling economy has been overshadowed by scandals underscoring rampant impunity and passage of the law could ease pressure on his party ahead of mid-term elections in June.

Earlier this month, the head of Mexico's federal water authority resigned after he and his family used one of the agency's helicopters for personal travel.

Last year, it was revealed that Peña Nieto, his wife and his finance minister had all bought or were using houses belonging to a government contractor involved in a consortium that won a high-speed train contract.

Fernando Belaunzarán, a congressman with the left-leaning Party of the Democratic Revolution (PRD), said the new law would put pressure on state governors to ensure spending is honest.