Kadhem's arrest and conviction came shortly after he wrote on his Twitter account about cases of payments, made by Bahrain authorities to candidates to encourage them to run in parliamentary elections held in Manama in November 2014.
The post on social media was regarded as "slandering the electoral process in the parliament," the source told RIA Novosti.
Another member of Al-Wefaq party, Sheikh Ali Salman was arrested on December 28, 2014 in Bahrain on charges of inciting a violent regime change through illegal practices and publicly insulting the Interior Ministry.
Al-Wefaq led anti-government protests by Shia muslims, which began in Bahrain in 2011 during the Arab spring. Shia Muslims, who form a majority in Bahrain, initiated the protests to achieve greater political freedom and equality as they claimed the regime under the Sunni Al Khalifa royal family infringes upon their rights.
After the crackdown on protest rallies by the authorities, Shia opposition deputies left parliament and boycotted last year's elections.