Employees at Toyota's auto assembly plants in southern India failed to return to work on Monday at the end of a week-long lockout after refusing to sign codes of conduct, their union said.
Although about 500 staff gathered outside the twin plants near Bangalore for the start of their shifts, they did not go in after managers insisted they sign the agreements, according to a local union chief.
"As we are against giving or signing any undertaking, none of us has entered the factory for the first shift which began at 6:00 am," Prasanna Kumar, president of the Toyota Kirloskar Motor Ltd Union, told AFP.
"The undertaking is against our rights as workers. We have a right to protect our interests and ensure that our welfare is not jeopardised."
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Operations had been expected to resume after Toyota announced at the end of last week that it had decided to lift the lockout following a meeting with labour groups which was chaired by a local government mediator.
However unions said at the time that the demand for employees to give a written undertaking of good conduct before resuming work was "harsh" and also demanded that Toyota reverse a decision to suspend 17 workers.
The Japanese firm, which is the world's largest automaker, suspended production on Monday of last week after long-running efforts to hammer out a new pay deal failed.
Toyota said some employees had resorted to deliberate stoppages of the production line, abuse and threats to supervisors and continuous disruptions to business for several weeks.
Company and union officials have been trying to agree a new contract for the past 10 months, with the government helping mediate negotiations.
Toyota Kirloskar Motor Ltd Union has demanded a pay hike of at least 4,000 rupees ($65) a month, while the company is offering only 3,050 ($50), citing difficult market conditions which have seen car sales in India fall almost 10 percent for first time in over a decade.
No company officials were immediately available for comment.
The two factories employ around 6,400 people and produce about 310,000 autos annually in a range of models including the flagship Camry sedan, the Corolla and the Prius hybrid, mostly for the domestic market.