Cook Islands High Commissioner John Carter has criticised his former National Party colleagues over proposed cuts to the Ministry of Foreign Affairs and Trade, according to Labour.
Labour Party foreign affairs spokesman Phil Goff said he had obtained a leaked email signed by 49 top Mfat diplomats, including Mr Carter - a former Local Government minister and long-serving National MP.
The email claimed a planned Mfat restructure could "undermine or even destroy" the agency's strengths, Mr Goff said.
"This letter is unprecedented. It is from our diplomats who are working on the frontline. They are deeply concerned that the proposed changes 'will severely curtail New Zealand's economic and foreign policy objectives' for years to come."
The letter was also signed by commissioners in the Americas, Asia, Europe, the Middle East, Africa and the Pacific, Mr Goff said.