Hike in Republic's US investment fuels pressure for business tax cut
Us companies doubled their investment in Republic to nearly $18bn (£11.4bn) in the first half of the year.
The 49% increase puts Ireland on the same level as Canada and the UK, according to an American Chamber of Commerce report.
US firms employ just under 100,000 people in the Republic with many attracted by a corporation tax rate of 12.5%, compared to a corporation tax rate of 26% in Northern Ireland.
The data will fuel the argument by business leaders calling for the UK Treasury to allow the Northern Ireland Executive powers to set our own rates of business tax in exchange for a cut in the Treasury block grant.
Last week Finance Minister Sammy Wilson said such a move was a least four years away while in the meantime, US companies are being drawn to our nearest neighbour.
In the past week, Twitter became one of a number of technology companies operating across the border including Google, Intel and Microsoft but many others like Pfizer and Abbot operate in the pharmaceutical sector.
Investment from the US is now worth $190bn (£121bn) and has grown five fold in 10 years.
The multinational sector also fuels exports which analysts believe is a key driver of growth in the Irish economy.
According to the figures, multinationals now account for one quarter of Irish Gross Domestic Product.