Beazley said Australia felt compelled to spy when he was defence minister because Washington refused to share the codes its F/A-18 fighters needed to identify potentially hostile aircraft.

In his farewell speech to parliament before retiring, Beazley said he went “up hill and down dale” in Washington trying without success to persuade top US defence officials to hand over the codes.

“In the end we spied on them and we extracted the codes ourselves and we got another radar that could identify them (enemy planes),” said Beazley, who was defence minister from 1984 to 1990 and later became deputy prime minister.

Australia is part of the US-led coalition in Iraq and Beazley said Washington remained Australia’s most important ally.

“But they are a bunch of people you have to have a fight with every now and then to get what you actually need out of them,” he said.

Beazley, who led the centre-left Labour Party to defeats against Prime Minister John Howard’s conservative coalition in 1998 and 2001, will retire at an election due before the end of the year.

A keen student of American history, he is widely expected to be appointed to a diplomatic post in Washington if Labour wins power.