A senior Tongan MP says he warned Parliament about the poor condition of a ferry which sank on Wednesday night.
Two bodies have been recovered since the Princess Ashika capsized: 93 people remain unaccounted for.
The Prime Minister and Transport Minister have repeatedly denied claims that the vessel was unseaworthy.
But Uliti Uata, who is also the chief executive of the Uata Shipping Line, says the ferry's design was not suitable for Tonga, where it would be in the open sea.
Mr Uata told Nine to Noon he did not believe the vessel was in a good condition.
Meanwhile, Prime Minister Feleti Sevele says it was up to the master of the Princess Ashika not to sail if he felt the vessel was not up to standard.
It's being claimed the captain believes the government knew the vessel was not fit for the water.
Mr Sevele says he's not prepared to comment on the claims, but says if he was a captain himself and knew of problems, he wouldn't have sailed.
Mr Sevele said he himself has seen a certificate of seaworthiness.
Royal Commission to be held
The prime minister announced on Monday night that work is underway to establish a Royal Commission of Inquiry.
A special sitting of Parliament will be held on Tuesday to work towards setting up the inquiry.
The ferry sank about 86km northwest of the capital, Nuku'alofa, en route to the Nomuka Islands group. The wreck has not yet been found.
Police in Tonga are still not confident they have an accurate manifest of those on the Princess Ashika.
Officers are working through a list of 149 names on the manifest, but say discrepancies have been found.