Toyota's plant problems comes in the wake of other, sometimes violent, labor disturbances, at Indian car factories in recent years.
In 2012, workers at India's top carmaker by sales, Japan's Suzuki Motor's unit Maruti Suzuki India, went on the rampage, killing one executive and injuring over 100 others in a dispute over pay and working conditions.
Toyota has appealed to the Karnataka state government to help end the row while the union has asked the state's labor ministry to protect its members' interests.
"Instead of resolving the issue amicably, management is misusing apprentices to make them work and has hired contract labor to do our job, which is skilled and involves stringent processes to ensure quality," Kumar said.
Even with a slowing car market, global vehicle manufacturers have been investing in India in the belief the country has great growth potential with just 15 out of every 1,000 people owning vehicles, according to industry figures, compared to saturated western markets.
Copyright Agence France-Presse, 2014