Prince William's career as an East Anglian Air Ambulance pilot may be in jeopardy, after it was found that the royal's every move could be tracked on a mobile phone app.

The Mail on Sunday discovered that terrorists would be able to target the Duke of Cambridge using a £2.99 app called flightradar24which reveals the exact location of his helicopter's position, direction of travel, speed and altitude as he carries out his duties as an air ambulance pilot.

The findings sparked a major security alert last night with experts warning that the information was 'intelligence gold' for terrorists and presented an "extraordinary risk" to the future king.

Subscribers can even receive alerts every time the Prince's East Anglian Air Ambulance helicopter, codenamed 'Anglia Two'takes off from its base at Cambridge Airport on a 999 rescue mission, while the app also reveals the precise location where the air ambulance lands.

The data is also available on the flightradar24 website for free as well as via the app.

While security measures are enforced during Prince William's official royal visits, no such screening process is in place when he arrives at the scene of an emergency.

Roy Ramm, a former Commander of Specialist Operations at Scotland Yard and an ex-head of the Flying Squad, called for immediate action to shut down the security loophole.

"Knowing the precise movements, altitude and speed of an aircraft in flight is intelligence gold for any terrorist. The ability to track a high-profile target like this presents a really serious risk," he explained.

"Even without expensive and sophisticated weaponry, there is the real danger that an inexpensive drone could be used to put any aircraft flown by William at risk. There is also the risk that a terrorist might simply open fire on his aircraft at low altitude with the kind of automatic weapon readily available to gangs in London. After all, the Prince is flying an air ambulance, not an armoured gunship."

Urgent action has reportedly been taken to remove information relating to the Prince's air ambulance from flightradar24.

Princess Diana's former personal protection officer Ken Wharfe added: "It's madness to have his flight details displayed in this way on an open website, and it should have been addressed long before now. Prince William is a target whether he likes it or not, and it just takes one nutter with a gun to act on this information and take a potshot.

"More generally, I would question the security risks of Prince William doing this job at all. It would be far preferable, if he's determined to fly helicopters, to do so in the secure environment of an RAF base, where he could be an instructor, rather than attending road accidents on the streets of King's Lynn."

Former head of the Met's Royalty Protection Squad, retired chief superintendent Dai Davies, said: "This would give me cause for concern and solutions need to be found by those in charge of the Prince's security. You always have to be aware of the advance of technology – which this illustrates – and the ability of these terrorist groups to think outside the box. You always, always have to be one step ahead."

Unlike William's civilian helicopter, most military aircraft do not show up on the tracking website, and neither does the US President's airliner, Air Force One.

Last year, the Japanese government made a successful appeal to flightradar24 have their own VIP aircraft details removed from the site.

A spokesman for the Bond Aviation Group, which operates the two East Anglian Air Ambulance helicopters, refused to say if the company was able to take any action to make Anglia Two invisible on tracking website, stating only that the company was aware of the flightradar24 app adding: "Bond cannot comment on the security arrangements."

Flightradar24 did not respond to requests for comment while Buckingham Palace and the Metropolitan Police, who are tasked with Royal protection, declined to comment about the app.

On July 16, Prince William carried out a successful air ambulance mission on his first day in his new job.

The 33-year-old, who is a pilot for the East of England Air Ambulance, set off on his first rescue mission, transporting medics to a location in Felixstowe, Suffolk, to assist a man who had suffered a heart attack.