British American Tobacco has lost its last court bid to gain access to Federal Government documents over plain cigarette packaging.

The company has been denied leave to appeal to the High Court to challenge a Federal Court decision over 1995 legal advice the Commonwealth received on plain packaging.

It comes after the High Court backed the Federal Government's legislation requiring all cigarettes to be sold in plain packets.

Quit Victoria's Kylie Lindorff says the implemetation of plain packaging is now guaranteed.

"Big tobacco had a huge loss in the High Court on Wednesday when plain packaging legislation was supported by the High Court," she said.

"Big tobacco has no other avenues left. Plain packaging will go ahead from December 1 and this is just icing on the cake in terms of public health outcomes for Australia."

The director of the McCabe Centre for Law and Cancer, Jonathan Liberman, says the company's bid to access the information was made under false pretences.

"It's another blow to British American Tobacco coming two days after a really big one in the High Court on the constitutionality of plain packaging," he said.

"It shows what they do. They continue to fight these thing through the court to tie up Government and court resources.

"The outcome again is as everyone expected. The Government has won another case with costs awarded to the Government."