Prime Minister Julia Gillard says she won't be intimidated by big tobacco after Philip Morris launched legal action to try to force the government to back down on introducing plain packaging for cigarettes.

Ms Gillard said the government was confident it could deliver its reforms and that they would make a difference to the number of people who smoke.

Standing firm ... Julia Gillard. Credit:AP

"We're not going to be intimidated by big tobacco's tactics, whether they're political tactics, whether they're public affairs kind of tactics out in the community or whether they're legal tactics," she told ABC radio.

"We're not taking a backward step. We've made the right decision and we'll see it through."