E tū journalist representative Brent Edwards, a former Radio New Zealand political editor, said Peters' attacks on the journalists could have a chilling effect on New Zealand journalism.
He said labelling journalists as political activists was disturbing and reprehensible, and similar to attacks on journalists in countries such as the Philippines, where press freedom and journalists' safety is taken much less seriously.
"As Foreign Minister, Peters should uphold his obligation to support press freedom and journalists' safety around the world, particularly in the Asia-Pacific region," Edwards said.
"If Peters continues to target journalists in New Zealand in an attempt to muzzle them, he does nothing for this country's reputation abroad as a healthy democracy which values and supports press freedom."
Peters is also seeking the journalists' phone records, notes and documents related to the superannuation story. Journalists can claim privilege under the Evidence Act to protect their sources, but Peters' lawyer Brian Henry has said he may challenge it.
Peters, 72, applied for his superannuation in March 2010 in person with his partner, Jan Trotman.
Peters claims that details of his superannuation overpayments - which he has since repaid - were passed on by Boyle to government ministers, and subsequently published by Newshub and Newsroom during the election campaign.
The National Party has refuted any suggestion it had any involvement in the leak.
Peters has claimed that the stories were designed to inflict damage on him in the election campaign. He says the public interest in the information did not outweigh his right to privacy, and the Government ministers should not have shared the information, nor should the media have published it.
Peters has declined to comment on the case, saying it was before the court. Prime Minister Jacinda Ardern has also declined to comment, other than to say that it is a "personal matter" for Peters.
A hearing is set down for March.
