Thousands of workers have staged rallies in 12 cities across Brazil to protest a proposed law that would allow companies to outsource their labor force.

The biggest rally occurred in Brasilia where some 3,000 demonstrators gathered in front of Congress hours before lawmakers were expected to vote on the law.

Except for a brief clash between police and demonstrators in Brasilia, the rallies across Brazil were peaceful. Most of them drew less than 500 people each.

In Sao Paulo, Brazil's financial and industrial nerve center, less than 1,000 people took part in the rallies.

The rallies were organized by the Central Workers Union, Brazil's largest labor union umbrella organization. It fears the law could lead to dismissals and the hiring of outsourced workers at lower wages.