Former British military pilots are being lured to China with large sums of money to pass on their expertise to the Chinese military, it is claimed.

Up to 30 former UK military pilots are thought to have gone to train members of China's People's Liberation Army.

The UK is issuing an intelligence alert to warn former military pilots against working for the Chinese military.

Attempts to headhunt pilots are ongoing and had been ramping up recently, western officials say.

A spokesperson from the British Ministry of Defence (MoD) said the training ​and the recruiting of pilots did not breach any current UK law but officials in the UK and other countries were trying to deter the activity.

"It is a lucrative package that is being offered to people," said one western official. "Money is a strong motivator." Some of the packages are thought to be as much as £237,911 ($NZ477,368).

The retired British pilots are being used to help understand the way in which Western planes and pilots operate, information which could be vital in the event of any conflict, such as over Taiwan.

"They are a very attractive body of people to then pass on that knowledge," a Western official said. "It's taking Western pilots of great experience to help develop Chinese military air force tactics and capabilities."

The UK first became aware of a small number of cases of former military pilots being recruited in 2019 which were dealt with on a case-by-case basis. The Covid-19 pandemic slowed attempts down, when travel to China was almost impossible but the attempts have now increased, leading to this alert.

"We've seen it ramp up significantly," a western official said in a briefing to journalists. "It is an ongoing issue." Current serving personnel are being targeted but none are thought to have accepted.

The pilots have experience on fast jets and helicopters and come from across the military and not just the Royal Air Force. They have flown Typhoons, Jaguars, Harriers and Tornados.

F-35 pilots are not thought to be involved although China is thought to be interested in them. Some of the pilots are in their late 50s and left the military some time ago. Pilots of other allied nations have also been targeted.

Officials said they were being recruited through intermediary head-hunters and cited a particular flying academy based in South Africa as being involved.

There was no evidence that any pilots have broken the Official Secrets Act or that they have committed any crime. The aim of the alert was to try and deter activity and inform current staff and industry partners and also remind personnel of their obligations to protect sensitive information.

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