The International Transport Workers' Federation (ITF) believes that the crew, still aboard the vessel 'Malaviya Seven', are now owed more than 600,000 pounds (USD 803,760).
It expects that the sale of the ship by an auction will cover the unpaid wages of the 11-member Indian crew.
The vessel's owner -- Mumbai's GOL Offshore Limited - is now in liquidation.
A writ had been served earlier which prevented the ship from leaving Aberdeen Harbour in Scotland.
"When a ship is found to be not in compliance with applicable convention requirements, a deficiency may be raised. If any of their deficiencies are so serious they have to be rectified before departure, then the ship will be detained," the Maritime and Coastguard Agency (MCA) said in a statement.
The Indian crew have been supported by local charities during their stay in Scotland, including Aberdeen's Catholic community.
They have refused to leave the ship over fears that they may never be paid and said while they have missed their families, they had found local people very welcoming.
'Malaviya Seven' chief officer Bamadev Swain told BBC Scotland: "My daughter keeps asking every now and then: 'When is papa coming back?' It's very difficult".
The 'Malaviya' was detained twice last year over unpaid wages, first in June 2016 after being contracted to BP.
The crew were eventually paid and the ship was released but it returned to Aberdeen under a different contract two months later and detained on identical charges.
Aberdeen Sheriff Court heard there has already been interest in the vessel, which will be advertised for sale around the world.
One estimate puts its sale price at 850,000 pounds (USD 1.1 million) and scrap value at 670,000 pounds (USD 896,955), while the union representing the crew believes it may be worth up to 1.1 million pounds (USD 1.47 million).
Aberdeen Harbour hopes to recover some of its costs to pay for the ship's long stay at the port but has said it will not take the funds out of the crew's wages.
The UK is part of a regional agreement known as the Paris Memorandum of Understanding on Port State Control under which information on all ships inspected is held centrally in an electronic database.