Apple may ultimately be hit by a €19 billion bill in Ireland on foot of a landmark EU ruling that the US technology giant received selective tax treatment in the Republic, according to Grant Thornton.

The European Commission ordered Ireland on Tuesday to recover unpaid taxes in this country from Apple for the years 2003 to 2014 of up to €13 billion, plus interest.

Grant Thornton tax partner Peter Vale estimates that the interest costs could come to a further €6 billion. However, Apple's chief financial officerLuca Maestri told reporters on a conference call on Tuesday afternoon that the company believes the interest bill will be "a significantly lower number".

“Given the nature of the Commission’s ruling, it is difficult to see Ireland having any option other than to defend its position. To do otherwise would result in Ireland bearing the brunt of negative coverage for a period of time, significantly impacting on our reputation,” said Mr Vale.

Both the Government and Apple said they intend to appeal the decision in court.

The EU’s decision, which found that Ireland’s “selective treatment” of Apple allowed the company pay an effective corporate tax rate of 1 per cent on its European profits in 2003, falling to 0.005 per cent in 2014.

The finding comes as Ireland finds itself at a “critical juncture” in terms of attractive foreign direct investment, following the UK’s decision to exit the EU, according to Mr Vale.

While the Revenue Commissioners are obliged, following the EU’s decision, to issue a tax bill to Apple, any monies collected will be held in escrow as the Government appeals the ruling.

“While assessing the likelihood of success at ECJ (European Court of Justice) level is difficult, there would appear to be a strong case supporting an appeal,” said Mr Vale. “In the meantime, while the tax to be collected is hugely significant, this is unlikely to be made available for public expenditure purposes pending the appeal result.”

Meanwhile, the American Chamber of Commerce Ireland said the analytical basis for the European Commission’s decision would appear to be at odds with generally accepted international tax and Organisation for Economic Co-operation and Development principles.

“It is difficult to see how it would withstand legal challenge,” American Camber said. It noted that the Commission has said explicitly that its ruling does not call Ireland’s general tax system or 12.5 per cent corporate tax rate into question.