"We issued the order declaring the strike illegal under the Prohibition of Industrial Disputes Act to both management and the union leader. If the workers continue the strike, we can issue show-cause notice and lodge a criminal case against them," said assistant labour commissioner M S Patel.
A Tata Motors official said that with the prohibitory order in place, the company hoped that normalcy will return.
The labour department has referred the matter to the industrial tribunal to decide if suspension of 28 workers was justified and if the striking workers should be paid wages.
Some 420 workers at the plant went on strike on February 23 demanding reinstatement of suspended workers. The company had first suspended two workers for indiscipline, and 26 others later when the protesting workers allegedly damaged new vehicles inside the plant.
Harpalsingh Zala, spokesperson of striking workers, said, "We have received the letter but have not yet decided whether to call off the strike. The matter is under discussion."
The Nano plant, which was originally to be set up in West Bengal, was later shifted to Gujarat. The company recently scaled down production of Nano cars to 2.5 lakh per year and announced plans to produce other models at the plant.