"All relevant issues, between workers and management have been referred for adjudication," the statement said.
As the union and management stuck to their stands, the state labour department issued the order to end the impasse.
"We sought to revoke suspension of 30 employees and let workers to resume duty without insisting on signing the conditional letter, but management declined," a union source said on anonymity.
Lockout was declared March 16 after wage revision talks between the management and the union failed and workers allegedly resorted to go-slow tactics affecting production.
Of the 6,400 employees, 4,200 are union members, while 2,200 are on contract.
"Daily production declined 50 percent to 350 cars from 700 cars, as the twin plants are operating in one shift with about 1,200 supervisors, technicians, apprentices and contract labourers," company vice-chairman Shekar Viswanathan admitted April 9.
Only 300 workers returned to work after signing the good conduct letter.
The two plants have an installed capacity to produce about 310,000 units annually.
"We were forced to declare lockout after production dropped to 70 percent during the first fortnight of March and due to unrest caused by a section of the workers, raising safety concerns of supervisors, managerial staff and plant machinery," Viswanathan said.
The 16-year-old joint venture rolls out a range of models, including Innova multi-utility vehicle, Camry sedan, Prius hybrid, Corolla Altis, Etios, Prado and Land Cruiser, with some of them imported as completely built units.
