Dozens of British ex-military pilots have traveled to China to train their Chinese counterparts, causing alarm among western defense officials.

"Without us taking action, this activity would almost certainly cause harm to the U.K. and our allies' defense advantage," a western security official told Sky News after the outlet released a report Tuesday that detailed China's efforts to recruit current and former British military pilots.

As many as 30 British pilots, mostly former fast jet and some helicopter pilots, are in China training their counterparts in the People's Liberation Army on how to defeat western military aircraft, the report said.

Defense officials are now scrambling to get control of a situation they say is "almost certainly enhancing China's military knowledge and capability" and poses "a threat to U.K. and western interests."

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Royal Air Force Planes

The Red Arrows perform over Scarborough where celebrations are taking place for Armed Forces Day 2022. (Danny Lawson/PA Images via Getty Images)

"Wow… that is appalling. What were they thinking?" asked a retired senior Royal Air Force officer in reaction to the news, according to Sky News.

China's recruitment effort is still ongoing, with officials saying the country is attempting to hire several more current and former British military pilots, luring them in with salaries of £240,000, or over $270,000. Beijing has also not limited their outreach to the British military, with officials warning China has also tried to recruit personnel from other western militaries.

China has used headhunting companies in their bid to attract qualified pilots, including the Test Flying Academy of South Africa, which has no affiliation with the South African government.

The situation has caused alarm within the British Ministry of Defence's Defence Intelligence service, which on Tuesday issued a "threat alert" aimed at warning the country's pilots against taking such jobs.

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Armed Forces Minister James Heappey told Sky News that the British military has been concerned about the issue "for a number of years" and that the country's service members currently working in China have been approached and warned against continuing their jobs.

"Don't go and train foreign air forces without checking with the MOD whether they are a foreign air force we want to see you train – would be a good rule," Heappey told Sky News.

Chinese helicopters and ships near Taiwan

Chinese military helicopters fly past Pingtan island, one of mainland China's closest points from Taiwan. (Hector Retamal/AFP via Getty Images)

Heappey said the government is currently working to make it illegal to ignore future warnings. 

"We are taking measures to dissuade current and former pilots from being recruited, and we want to avoid any perception by China that our previous silence on this matter is misinterpreted as our acceptance or approval of this activity," a western security official told Sky News.

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Officials have been unable to figure out the exact number of British service members who are working in China or how many current and former members are being recruited, though they believe "it is certainly more than just a trickle."

Officials highlighted just how dangerous the situation is, noting that the former pilots are not just training Chinese military members how to fly, but teaching them how to counter western and NATO warplanes.

"It's not training Chinese pilots on western jets. It's taking western pilots of great experience to help develop Chinese military air force tactics and capabilities," one official told Sky News. "It's really the Chinese having an understanding of what the latest generation of tactics and approaches and capabilities would be, were the Chinese military to get into situations coming up against those types of assets."

In a statement to Sky News, the British Ministry of Defence promised action was underway to prevent security breaches in the future while warning service members who have taken jobs that they are still subject to the Official Secrets Act.

China's Xi Jinping at meeting wearing black suit

Chinese President Xi Jinping (AP Photo/Ng Han Guan)

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"We are taking decisive steps to stop Chinese recruitment schemes attempting to headhunt serving and former U.K. Armed Forces pilots to train People's Liberation Army personnel in the People's Republic of China," the spokesperson said.

"All serving and former personnel are already subject to the Official Secrets Act, and we are reviewing the use of confidentiality contracts and non-disclosure agreements across Defence, while the new National Security Bill will create additional tools to tackle contemporary security challenges – including this one."