BOGOTA — Colombians voted on Sunday in a referendum on hardening punishments for corrupt officials and business figures, after the congress proved reluctant to implement stricter anti-graft measures.

Some 36 million voters were called to the polls amid an ongoing bribery scandal involving Brazilian construction giant Odebrecht that has engulfed the region.

To be approved, the referendum requires one-third of voters to take part, potentially a problem in a country with historically low election turnout.

The measure includes seven proposals, from cutting high-ranking officials’ salaries to imposing term limits to eliminating house arrest as a punishment.

While mostly aimed at cracking down on abuses by public officials, the initiative would also make private contracts with the state more transparent and prohibit companies convicted of corrupt practices from dealing with the public sector.

"This is a very important day, where we have voted to express our rejection against corruption," said President Ivan Duque. He said the issue involved not a political or ideological one but rather "the commitment of an entire country."

Senator and Green Alliance leader Claudia Lopez, a backer of the referendum, said on radio that if Congress fails to pass the new rules within a year, Duque will be able to install them by decree.

Corruption in Colombia, she added, is "more profitable than drug trafficking."

One university study found that, from 1991 to 2011, corruption cost Colombia 4 per cent of its GDP. — AFP