Former MP Jamil Kazem tweeted to attack the kingdom’s government over reported bribes it paid for candidates to take part in the legislative elections.
Al-Wefaq said his conviction, including a fine, showed "the regime does not believe in political dialogue but rather in arbitrary procedures against those who do not share its opinions."
The sentencing comes as al-Wefaq chief Sheikh Ali Salman, whose arrest on December 28 sparked clashes between protesters and security forces, remains in detention.
Authorities in the kingdom, which is home to the US Fifth Fleet, have said his detention has been extended pending a probe into charges including seeking to change the regime by force.
Bahrain, with Saudi Arabia’s help, crushed peaceful pro-democracy demonstrations that began on February 14, 2011 inspired by Arab uprisings elsewhere, but has yet to resolve the conflict between the population and the monarchy oppressing them.
The kingdom has since banned all protests in the capital Manama, and has been violently suppressing nationwide, peaceful protests demanding social and political reform.
Hundreds have since been arrested and put on trial for criticizing the government, human rights groups say.
