Korea's largest fishing company, Sajo Oyang Corporation, tried to gag Indonesian crew by buying them off with a "peace agreement".

The agreement, obtained by the Sunday Star-Times, shows corporation official Oh Gwan Yeol offered some of the 32 crew US$7300 to withdraw complaints of fraud and assault lodged with Korean courts and New Zealand Immigration Service.

The payment is about a third of the $US23,000 owed for the six months they worked into their two-contract before walking off the Oyang 75 in Lyttelton last year protesting against inhumane conditions aboard.

The agreement says there will be "no more invoices and claims whether criminal or through any court of justice".

Christchurch-based lawyers for the corporation said 28 crew had now signed the agreement but the amount of payments transferred into their Indonesian bank accounts varied.

The Korean Coast Guard has applied to lay charges against the corporation's chief executive and two Korea-based managers and shipping agent relating to forged wage documents. The crew's officers face charges including assault and sexual assault.

The crew's Tauranga-based lawyer, Craig Tuck, said the so called "peace agreement" could be considered an attempt to pervert the course of justice.

The crew effectively haven't been paid since they joined the Oyang 75 in January 2011 because their first 90 days' wages of $260 a month went to their Jakarta-based shipping agent.

"There's nothing to stop the Korean or New Zealand police taking a prosecution but there is the practical reality of getting witnesses to provide live evidence," Tuck said.

Four Oyang 75 officers were last month fined $420,000 for fish dumping and filing false catch returns. The corporation paid a $900,000 bond to take the 68m trawler, worth up to $9.6 million, out of New Zealand. It is currently in Mauritius.

Tuck has applied to recover some of the $917,000 the crew are owed through the forfeited ship, if it returns to New Zealand.

Emails obtained by the Sunday Star-Times show police decided last year not to lay charges over the crew's complaints they had been physically and sexually abused because it was a "workplace issue". Police believed a criminal trial would be "futile" and the "hundreds of hours" a case could take to prepare was not a "prudent use of police resources and would not be in the public interest".

Officer in charge, Detective Senior Sergeant Greg Murton, said action by Korean authorities did not change his decision but any new evidence would be considered.

Yeol is known to New Zealand officials after he fronted a coroner's inquest into another of the corporation's fishing vessels, the Oyang 70, which sank off the Otago coast in 2010 with the loss of six crew.

Christchurch police are investigating the validity of documents provided by the corporation to the inquest after they were referred from the Coroners Court.

Immigration's general manager of intelligence, risk and integrity, Peter Elms, said a New Zealand prosecution for workplace assault was difficult because the alleged offending occurred outside New Zealand waters.

Immigration was expecting a report from the Korean authorities over the next couple of weeks.

However, it was too early to say whether New Zealand would look at laying its own charges against the corporation.

Immigration was "sufficiently concerned" about the actions aboard Oyang 75 and within Sajo Oyang that it last year suspended the issuing of any further work visas, he said. The corporation had since moved its vessels out of New Zealand waters.

Immigration has commissioned a second forensic audit of wage payments claimed by the corporation after an earlier audit by PricewaterhouseCoopers couldn't verify the documents it provided.

The gagging agreement would not have any impact on whether New Zealand authorities prosecuted, Elms said.

"We'd need to be satisfied in future that any company operating in New Zealand waters had transparent processes in place to make sure all crew were paid what they should be paid and treated fairly.

"Until we have that confidence, we will not be issuing visas to foreign charter vessels," Elms said.

- © Fairfax NZ News