Carr offers government advice on China

What's the difference between a best friend, an oldest friend and your closest friend?

Quite a bit in the tricky world of diplomacy, where the choice of words can mean the difference between a compliment and a snub.

Former foreign minister Bob Carr seems to think the Abbott government is in need of a few lessons, warning it risks offending China if it keeps up its recent form on the world stage.

Mr Carr said since the election, Foreign Minister Julie Bishop had described Japan - which is engaged in a row with China over a territorial dispute - as "our best friend in Asia".

But until now, Mr Carr said foreign ministers had described Japan as Australia's "oldest friend" in Asia, or that it had "no closer" friends.

Prime Minister Tony Abbott went further in late November when he described Australia as "a strong ally of Japan".

"We are not officially allies," Mr Carr wrote in The Australian Financial Review on Saturday, adding Australia had previously referred to Japan as "friend" or "partner".

Mr Carr warned such signals sent the wrong message to a country with whom Australia wants to sign a free trade agreement within a year.

It was "hardly cutting-edge diplomacy" for Ms Bishop to use a trip to Washington to declare China counted less when it came to trade and investment than the US, he said.

"My reading of China is that they accept Australia as a close ally of the US and that we will always be drawn to America," said Mr Carr, who resigned as a Labor senator in October.

"But they seem to want that we not shove this fact quite so squarely in their face."

He also criticised the government for overlooking two "measured options" for dealing with China's declaration of a no-fly zone in November.

Ms Bishop was publicly upbraided by her Chinese counterpart for "irresponsible" comments when she voiced concerns about the air-defence zone declared over a disputed island chain.