Shane Rattenbury.

Confident ... Shane Rattenbury believes the Greens can capture an extra 400,000 votes at the next federal election. Photo: Rohan Thomson

The Australian Greens are trying to raise a multimillion-dollar election war chest, telling donors that the party can boost its vote by 25 per cent at the next federal election.

The party has declared a $3 million "national fund-raising target" and says research indicates it can increase its 1.6 million votes at the last national poll to more than 2 million at the election next year.

Despite most published opinion polls showing a slump in Greens support since the 2010 election, the fund-raising material distributed in Canberra by ACT Greens minister Shane Rattenbury includes claims the party can capture an extra 400,000 votes countrywide. The latest Nielsen Poll has the Greens on 10 per cent of the vote nationally, down from the 11.8 per cent it attracted in 2010, an all-time high.

The last time the Greens faced the voters was in the ACT election in October, when they suffered a swing against them of nearly 5 per cent, losing three of their four members in the territory's Assembly.

But Mr Rattenbury is undeterred, sending out fund-raising material to Canberra supporters asking for money to allow the party to "hit the ground running in 2013".

"We now turn our attention to the federal election … there is no doubt this will be a challenge for us," the remaining Greens MLA wrote.

"We need to rebuild our resources following the ACT election and prepare for the federal campaign ahead.

''Our research to date indicates that 2 million votes across the country next election are achievable.''

"To help us reach this goal, we've set a national fund-raising target of $3 million," Mr Rattenbury wrote.

"Now is the time to start building this capacity to take on the old parties in 2013.

Liberal ACT Senator Gary Humphries, the man whose seat has been targeted by the Greens in the territory at the past several elections, poured scorn on the Greens claims on Tuesday.

Senator Humphries accused his opponents of distributing "dodgy polling".

"Only a couple of weeks ago I predicted the Greens would release rounds of dodgy polling in the lead up to the federal election - well here is the first of them,'' he said.

''The Greens' claim goes against all evidence to the contrary; I find the announcement bizarre to say the least.

''People will vote against the party who raise their cost of living … raising living costs is in the Greens' DNA."