Mr Williamson claimed he was "engulfed in flames and sustained burns to 30 per cent of his body" when he tried to light a barbecue while stationed at Defence Establishment Berrimah as part of Marine Rotational Force — Darwin.

He claimed "other military and civilian personnel of the United States Marine Corps were aware of the fault [with the barbecue]" and "at least two of those persons informed a member of the Australian Defence Force".

But on Wednesday, the Northern Territory Court of Appeal overturned an earlier Supreme Court ruling that knocked back the US government's claim to immunity from civil action in Australian courts.