Mexico City, Mexico - Mexico's ruling party has proposed holding a referendum next year to reduce the size of Congress, which could strengthen its own hand and streamline legislative decision-making.

Mexico's Congress is made up of the lower house with 500 members and a Senate with 128 members. Both houses have a minority of lawmakers elected through proportional representation and the rest by a relative majority, in which the candidate with the most votes wins.

The idea is to slash the number of lower house legislators elected by proportional representation to 100 from 200, said Cesar Camacho, the head of President Enrique Pena Nieto's Institutional Revolutionary Party, or PRI.

"We think there are too many lawmakers. This would reduce public spending, make agreements easier and make Congress more efficient," Camacho told a news conference.

Pena Nieto proposed reducing the number of lower house deputies to 400 from 500 during his 2012 election campaign.

Such a reform would benefit the PRI, which ruled Mexico continuously from 1929 to 2000, because it relies less on proportional representation in Congress than other parties. By contrast, such a move would hit the smallest parties.

The plan also proposes getting rid of the 32 senators currently elected by proportional representation.

The PRI needs to collect 1.6 million signatures for the referendum to proceed. If the PRI can muster them, the referendum would be held during mid-term elections in July 2015, when Mexico is due to renew its lower house as well as nine state governors and hundreds of local mayors.

The initiative follows a recent political reform that creates scope to hold more referendums. Leftist parties hope to overturn Pena Nieto's signature reform - the opening of the oil and gas industry to private capital - via referendum in 2015.