Leaked documents suggest the World Trade Organisation has upheld Australia's cigarette plain packaging laws.

The decision has not been officially announced, but a confidential draft of the ruling obtained by US media outlets suggests international tobacco companies have failed to argue that the plain packaging infringes on protected trademarks.

Former health minister Nicola Roxon says it is a hard-fought victory for public health advocates.

“I'm absolutely thrilled with the news today because it's a big win for Australia, both for our previous government [and] also for the current government that continued to fight so hard,” she said.

“And now the results are three to Australia, zero to the tobacco industry, and I call that a big win.”

Tobacco giant Philip Morris used investor-state dispute settlement provisions in a 1993 Hong Kong trade deal to argue that the Australian laws inhibited its ability to make money, going as far as challenging the constitutionality of plain packaging laws in the High Court.

“We had a fight in the High Court, which we won. We had a fight in Hong Kong with Philip Morris that we won. We've had a fight in the WTO,” Ms Roxon said.

“It's time for them to call it quits. They can't keep fighting unless they think that simply by fighting they'll scare people off.”

Research has shown that the plain packaging laws are linked to a reduction in the rate of people taking up smoking.

Ms Roxon says other countries should take Australia’s lead and enact similar laws to reduce smoking rates.

“Governments of all colours and a lot of advocacy in the community has meant that we've been able to withstand pressure [from tobacco companies], but now other countries will take heart from this,” she said.

“I don't think the industry, even when they throw everything they can at it, will be able to stop governments trying to intervene and reduce people getting addicted to this very dangerous product.

“Australia can be really proud that we've been leading the way on this front.”

Trade Minister Steve Ciobo has not confirmed nor denied the leaked decision.

“WTO dispute settlement cases remain confidential until finalised and circulated to WTO members,” he said.

“As the interim report remains confidential it would not be appropriate for the Government to comment at this time.”