Four former New Zealand Defence Force personnel have been warned their decision to work for a South African flight school will likely impact any future employment with the force.

The UK has cracked down on former military pilots working at the Test Flying Academy of South Africa, suspected to be an intermediary for China's People's Liberation Army to recruit pilots.

A spokesperson for Defence Minister Peeni Henare said the Defence Force is aware of four former staff who quit to work for the academy, and they have probably jeopardised any future attempts to get a national security clearance.

The British government in October announced a crackdown on former military pilots working for intermediaries, including Test Flying Academy of South Africa.

"One of the four of the individuals was spoken to, and this happened in October as they were the only one who maintained a security clearance with [the Defence Force] at the time," a New Zealand Defence Force spokesperson told Reuters.

The academy has previously responded to the British crackdown with a statement on its website, saying all of its activities were legal. A previous contractor there, former US marine pilot Daniel Edmund Duggan, was arrested in New South Wales in October at the request of the US government. His case will be in court this week. He denies breaching the law.

The New Zealand Defence Force spokesperson added it had also advised staff on 23 October about the academy, reminding them of their obligations to security and to their security clearance under the government's Protective Security Requirements.

Henare's office has asked for advice on the situation, and whether more needed to be done. A spokesperson said Henare was assured the Defence Force had taken all practical steps to ensure there was no risk to sensitive information being released.