US multinationals operating here paid effective corporation tax rates of 2.2pc in 2011, a new study shows.
The study from Trinity associate professor finance James Stewart is based on figures from the US Bureau of Economic Analysis.
It also suggests that the effective tax rate is well below the official 12.5pc rate, despite Government claims.
The paper's finding, reported in today's Irish Times, come as Ireland comes under ongoing fire over its low corporation tax.
Just last week, Taoiseach Enda Kenny faced questions in Paris over Yahoo's decision to transfer its finance operations here.
In response, the Taoiseach quoted a PwC/World Bank report which found an effective rate of 11.9pc here.
The Organisation for Economic Cooperation and Development is examining ways to close corporate tax loops like the so-called "double Irish" and the "Dutch sandwich."
Speaking on RTE's Morning Ireland today, Professor Stewart dismissed the PwC report as one based on "a fictitious or hypothetical" ceramic pot-making firm that was not relevant in the calculation of effective tax rates.
However, Feargal O'Rourke, head of tax at PwC, defended its report and said there was a "hole the size of the grand canyon" in Professor Stewart's study.