"Though the Central Government is seized of the matter, its efforts to get the imprisoned fishermen released do not seem to have yielded the desired results," Karunanidhi said in a letter to Prime Minister Manmohan Singh.
Requesting the Prime Minister to instruct all concerned to take sustained efforts to ensure their release, he said the fishermen families have been undergoing "untold miseries" for their day-to-day livelihood.
The fishermen have been languishing in the prison in Iran for more than 50 days and are refused food, drinking water and medical facilities, he said, adding "they have been facing inhuman treatment at the hands of the prison authorities of Iran."