Australia's tobacco plain packaging laws are a legitimate public health measure, according to a World Trade Organisation dispute panel ruling reported by Bloomberg.

It cited two people close to the situation as saying the panel had rejected a case made by Cuba, Honduras, Dominican Republic and Indonesia, which argued the laws constituted illegal barriers to trade.

Such a ruling from the WTO has been widely anticipated as giving a green light for other countries to roll out similar laws, not only on tobacco but also on alcohol and unhealthy foods.

The ruling is not expected to be published until July, but a confidential draft has been circulated to parties in the case, Bloomberg reported.

Spokespeople for the WTO were not immediately available for comment.

Former Australian health minister Nicola Roxon, who introduced plain packaging for cigarettes, said the decision should encourage other countries to follow suit.

"We've already seen a large number of countries introduce or take steps to introduce plain packaging, so it's a really significant international outcome," she said.

A spokeswoman for British American Tobacco declined to comment on the ruling until it was publicly released, but suggested the complainants would keep fighting.

"As there is a high likelihood of an appeal by some or all of the parties, it's important to note that this panel report is not the final word on whether plain packaging is consistent with international law," she said.

A spokeswoman for Japan Tobacco International also declined to comment on the ruling, but the fact that the draft had been leaked was disconcerting and a breach of WTO rules.

"Such breaches completely undermine the integrity of the process, which has not yet run its full course," she said.

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Some trade experts said they expected the arguments on trademarks to go Australia's way, but the complainants were battling to discredit the data used to support Australia's case.

Australia had the backing of the World Health Organisation, and many other countries began announcing similar legislation, a sign that they expected the WTO to rule in Australia's favour.

The plodding pace of WTO decision-making prompted Australia to complain that its challengers were deliberately stalling the proceedings, producing a "regulatory chilling" effect on other countries wishing to follow its example.

Britain, France and Hungary went ahead with their own legislation, while Ireland, Canada, and South Africa are considering following suit.

Reuters