The documents show the newly-formed Alliance of Australian Retailers, which was set up last month to fight the planned introduction of plain cigarette packaging in Australia, has received over A$5 million (NZ$6.3 million) from the three biggest tobacco giants.
The companies have never denied supporting the group, but the leaked documents suggest they were involved in designing the campaign from the very beginning.
Broadcaster ABC obtained internal emails, invoices and contracts that revealed tobacco companies had hired a public relations firm which told them to launch a campaign hidden under a third party like a retailers association.
The Alliance of Australian Retailers was formed less than three months later, on the same day it received over A$5 million from the three biggest tobacco companies.
The revelation comes just months after a recently-established New Zealand group, the Association of Community Retailers (ACR), was also revealed to have received support from the tobacco industry.
The ACR, which was critical of the New Zealand Government's tobacco price hikes in April, has rejected suggestions it was backed by tobacco cash and said it was entirely funded by its small retailer members.
But Imperial Tobacco's New Zealand sales and marketing director, Tony Meirs, told a select committee in May that his company had provided public relations advice to the group through a PR agency, Omeka Public Relations.
Bloggers have revealed a number of other links between Omeka Public Relations, the ACR and Imperial Tobacco.
The ACR was found to have shared a postal address with Omeka Public Relations, whose managing director Glenn Inwood helped retailers to establish the group.
Mr Inwood also has links to a company which distributes press releases from Imperial Tobacco.
He has maintained the ACR receives no funding from tobacco companies or himself but purely from members' subscriptions.
The Australian leaked documents, meanwhile, reveal evidence of link between tobacco companies and the Alliance of Australian Retailers.
Professor Mike Daube of the Council on Smoking and Health said the leaks were the most damaging in the country's history.
"What this tells us is that, far from being the innocent retailers campaign that it pretends to be, this is a campaign that has been developed, masterminded and run to the finest detail by the Philip Morris company ... in association with British American Tobacco and Imperial," he told the ABC.
In a world first, Australia plans to require cigarettes to be sold in plain packages carrying large, graphic warnings against smoking by 2012.
Philip Morris contacted Melbourne public relations firm The Civic Group for advice on how to fight the government's plan months before the Alliance of Australian Retailers existed, the ABC reported.
The Civic Group then told Philip Morris to launch an aggressive and intense campaign that builds "concern among the targeted decision makers that the campaign will not cease, it is likely to increase and that it will extract a political cost".
Its proposal recommended using third parties like retail groups to sell the message, the leaked documents show.
The Alliance of Australian Retailers was later formed in August, purporting to represent thousands of corner stores and shopkeepers.
On the day the alliance was formed, documents said it received A$1,080,860 funding from Imperial Tobacco Australia, A$2,200,000 from British American Tobacco, and A$2,161,720 from Philip Morris.
Philip Morris also paid The Civic Group a A$200,000 a month retainer to help manage the alliance, according to the documents.
A Philip Morris statement said it was disappointed the documents appeared to have been obtained by illegitimate means.
British American Tobacco said it continued to proudly support the alliance.
