The Tánaiste has pledged to increase tax bands in line with inflation and said workers on the average industrial wage will not be taxed at the higher rate.
Ms Harney said she was seeking such measures, which are not in the Programme for Government, within the lifetime of the coalition with Fianna Fáil.
Senior party sources said last night that Ms Harney wanted to introduce such changes sooner rather than later. However, they would not say whether Ms Harney had already raised the proposals in discussions with her Fianna Fáil colleagues.
While the Government has been heavily criticised over stealth taxes since its re-election in 2002, better tax returns since the start of the year suggest that Ministers may have room for manoeuvre on the tax in the run-up to the next Budget.
A move to index-link tax bands would reverse the trend in recent budgets in which the Government failed to increase the bands in line with inflation.
In the most recent budget, the failure to apply indexation to the bands resulted in an additional 50,000 workers being taxed this year at the higher rate of 42 per cent. Protection for average industrial wage earners from paying the higher rate would keep single and widowed earners, with no dependants, within the standard 20 per cent band.
The standard rate threshold for such workers is currently €28,000, only slightly higher than the €27,900 average industrial wage last year.
Ms Harney described such measures as PD policy "commitments" in her opening address last night to the Progressive Democrats' annual conference.
"These are the tax results we want to achieve in this Government," she said in Killarney.
In a speech centred on the PDs' taxation policy, Ms Harney said the Opposition figures who condemned the number of people paying tax at the higher rate were "the same people who fought our tax cuts every step of the way down". Ms Harney said people were "completely wrong" to say her party's agenda had already been achieved.
"We believe in low tax because low tax brings more economic activity, more resources, more jobs," she said. She criticised the "smaller parties" of the Opposition who, she said, wanted "massive tax increases" but did not seem to know it themselves.
"They talk instead about increasing tax as a proportion of gross domestic product - as if no-one would actually have to pay for it," she said. "If you want something cut down, tax it. I don't think we should treat jobs like we treated plastic bags."
In an implicit reference to the resumed discussions on the draft EU constitution, in which the Government will face renewed pressure to remove the national veto on taxation, Ms Harney said such a measure would signal the "death of democracy".
