Tonga's Solicitor-General says the Crown is appealing against what it considers light sentences given to crew of a ferry which sank in 2009 with the loss of 74 lives.
In a trial earlier this year, Princess Ashika skipper Viliami Tu'ipulotu was jailed for four years, but the sentence was suspended for three-and-a-half years.
First mate Semisi Pomale was jailed for five years, suspended for three-and-a-half years.
Both were convicted of a number of charges, including manslaughter by negligence, Radio New Zealand International reports.
Solicitor-General Aminiasi Kefu says his office contends that the judge erred in granting such lengthy suspensions.
Mr Kefu says the former chief executive of the Shipping Corporation of Polynesia, John Jonesse who was jailed five years, is appealing against his conviction and sentence.
Mr Kefu says it is possible the New Zealander could get a similar partially suspended sentence.