BIG tobacco has opened up a new front in its war against Australia's plain packaging laws.

The World Trade Organisation has revealed that within hours of Australia's victory in the High Court on Wednesday the former Soviet republic of Ukraine upgraded to formal a complaint against Australia's law and demanded the establishment of a disputes panel.

Australia will need to argue its case before the WTO in a process that could take up to 14 months. An adverse finding would put Australia in breach of WTO rules requiring compensation or a backdown.

"It's a remarkable coincidence," Trade Minister Craig Emerson told The Age. "The Ukraine was engaged in informal talks with us up until the High Court win, and then went formal."

Asked whether he thought big tobacco companies were behind the decision, Dr Emerson said he was "not aware of tobacco being a big industry in Ukraine, so one would wonder why it would have a big interest in this". Once a substantial tobacco grower, Ukraine now imports tobacco to manufacture cigarettes, which it exports to Europe.