The agreement, which Reuters reported earlier this month, comes a year after the three countries established their first major defence industry collaboration by merging the separate next-generation fighter efforts of London and Tokyo.

The parliaments of each country must ratify the agreement, which aims to see the combat aircraft in flight by 2035. The joint development phase of the programme is due to launch in 2025.

Both the joint government headquarters of the Global Combat Air Programme (GCAP) and its industry counterpart will be based in Britain. The government organisation's first chief executive will come from Japan, while the first leader of the business organisation will be from Italy, Britain said.

"Our world-leading combat aircraft programme aims to be crucial to global security and we continue to make hugely positive progress toward delivery of the new jets to our respective air forces," British defence minister Grant Shapps said.

Shapps and his Japanese and Italian counterparts, Minoru Kihara and Guido Crosetto, met in Tokyo on Thursday.

The supersonic stealth jet will feature a radar that can provide 10,000 times more data than current systems, the British government said.

Britain's BAE Systems, Italy's Leonardo, European missile maker MBDA and engine maker Rolls-Royce are involved in the project.

Reuters has previously reported that Japan's Mitsubishi Heavy Industries, Japanese avionics manufacturer Mitsubishi Electric Corp, and engine makers IHI Corp and Avio Aero are also involved.

(Reporting by Kylie MacLellan; Editing by Angus MacSwan)