Hackers have broken into the US Department of Defense’s $300bn (£206bn) Joint Strike Fighter programme, which is partly funded by the UK.

The Joint Strike Fighter project is a development initiative to replace ageing fighter aircraft with next-generation F-35 planes.

The F-35, with its advanced airframe, autonomic logistics, propulsion systems and firepower, is to be the next fighter jet for the Royal Navy and Royal Air Force. The UK has invested $2bn (£1.37bn) in the F-35’s development – the largest single contribution from the programme’s eight partner nations.

US officials believe the attacks could have originated in China, having tracked the intruders to known Chinese internet protocol addresses, according to a Wall Street Journal report.

The hackers copied data relating to the aircraft system design by exploiting network vulnerabilities in computer infrastructure belonging to contractors helping to build the new planes.

Lockheed Martin, the lead contractor on the project, could not immediately be reached for comment.

The hackers encrypted the data they stole to stop officials knowing the extent of the breach. However, according to reports the most sensitive design information, such as flight controls and sensors, was not touched because it resides on computers not connected to the internet.

The UK last month purchased its first three F-35s, signaling its commitment to the upcoming test and evaluation phase of the project. The UK plans to eventually buy 138 F-35s.

More than 100 British companies have been involved in the programme, including BAE Systems, which produces the aircraft’s aft fuselage and tails, and Rolls-Royce, which is developing and manufacturing the shaft-driven lift fan and other propulsion components.