The final report into the sinking of the doomed Tongan ferry Princess Ashika claims the country's government failed its people by buying a boat that was obviously unseaworthy, according to leaked information.

A 54-day Royal Commission of Inquiry revealed a raft of possible explanations why the Princess Ashika rolled and sank at midnight on August 5 last year, killing 74 men, women and children.

An interim report published in November 2009 revealed the commission needed to consider additional evidence and hear more witness accounts.

The inquiry was adjourned indefinitely on March 12 and a report was handed to the king of the South Pacific nation on Wednesday morning.

A spokeswoman for The Women's and Children's Crisis Centre in Tonga, Ofa ki Levuka Guttenbeil Likiliki, said yesterday the report had not been made public, but its contents had been leaked.

"The king has been presented with a copy and also the members of parliament ... (but) none of the media as of this morning had been given a copy of the report," she said.

"The report has to go through the Privy Council first before it's released to public.

"However ... it has been leaked already to overseas media."

Ms Levuka Guttenbeil Likiliki said the council wasn't likely to assess the report until next Tuesday.

Radio New Zealand's Tonga correspondent, Mateni Tapueluelu, told the network the report placed responsibility for the tragedy on the country's government.

"It does zero down on the former minister of transportation, Paul Karalus, saying that he lied - he knew when he provided false information to various authorities, beginning with the king, the prime minister, the government and parliament and even to the media," Ms Tapueluelu said.

"And the commission is saying that he knew at the time the information that he told the king, that due diligence was done on the Ashika, was false."

The inquiry heard the vessel was severely rusty and seawater poured into the cargo hold as it made its way from the Tongan capital Nuku'alofa to an outlying island.

Giving evidence at the final day of the inquiry, Mr Karalus admitted he never saw any paperwork that proved the Princess Ashika was seaworthy, despite telling both the prime minister and king he had done so, the Matangi Tonga website reported at the time.

Mr Karalus resigned six days after the tragedy.

Ms Levuka Guttenbeil Likiliki said it was vital for the report, written in English, to be translated into Tongan and made readily available.

"Not everyone could go to this inquiry ... (and) this report means a lot to Tongans all over the country because for them it's the first step in calling for justice and accountability," she said.

"It will offer closure and it will also provide a transparent account of the findings, which will hopefully be able to be implemented and used."

In March police charged Shipping Corporation of Polynesia managing director New Zelander John Jonesse, Princess Ashika captain Makahokovalu Tuputupu and first mate Viliami Tu'ipulotu with manslaughter and with sending an unseaworthy vessel to sea.

Mr Jonesse was barred from leaving Tonga on Wednesday after an emergency sitting of the Supreme Court overturned an earlier decision to let the New Zealand businessman leave.