He adds that Ireland's low 12.5% corporation tax rate is still a large factor in attracting foreign businesses to the country.
"It's hugely important for a couple of reasons," says O'Donnell. "One, of course, is the low rate – and the message that it is staying low is vital. It should not even move, because once it starts to move that would send a negative psychological signal to corporations. The corporation tax is the bedrock, but it is also important that Ireland has a very transparent tax system, which works to our advantage. As well as manufacturing, Allergan runs a lot of its financial services in Ireland because of our tax system."