At present, the environment secretary of the Delhi government is holding the additional charge of the chairman's post.
A vacation bench headed by Justice RS Rathore said the post of the chairman is a "sensitive and responsible" post as the entire environmental status of the state depends on the functioning of the pollution control board.
The tribunal warned the Delhi government that in case it fails to complete the appointment process of the chairman, then the person now holding the post shall cease to function.
The green panel also noted that in most of the state pollution control boards, the post of the chairman is held by persons lacking in qualification or experience in the field of environment.
"The tribunal cannot remain a silent spectator in respect of improper and illegal working of pollution control board and its consequence and repercussion to the public at large.
"It is rather strange that despite of more than sufficient time having been given by the tribunal, the state did not take steps to implement the judgement passed by the tribunal on August 24, 2016," the bench, also comprising expert member S S Garbyal, said.
The direction came after the counsel for the Delhi government said that requisite steps have been taken by the board to appoint the chairman and the issue is awaiting Central Pollution Control Board's nod.
He assured the bench that the process would be completed soon.
The NGT had earlier barred the chairpersons of nine state pollution control boards (SPCBs) from functioning with immediate effect for not being appointed in consonance with the judgement of the tribunal.
The green panel had in August last year asked the state governments to fill the vacancies in the boards as per the guidelines laid down by it and file a report.
Earlier, the NGT had issued notice to the states and chairpersons of their pollution control boards which have not been appointed as per the norms laid down by it.
It had asked them as to why they should not be directed to stop functioning as chairmen as they were not appointed in consonance with the judgement of the tribunal.
The green panel, which had issued a slew of guidelines for appointment to the posts of the chairmen and member secretaries, had in August said the nominations should be of persons who have "special knowledge, practical experience or qualification in environment protection studies" and not on the ground of their association with a state government.