Food company Glanbia invested more than €1bn in Luxembourg-based subsidiaries that employ no staff and exist simply to reduce its tax bill.

Leaked documents obtained by the International Consortium of Investigative Journalists show Glanbia and other Irish companies were among hundreds of firms to negotiate agreements with tax authorities in Luxembourg.

These documents leaked from accounting firm PwC and obtained by the ICIJ run to 28,000 pages and detail what are known as advanced tax agreements.

Those secret deals with authorities in Luxembourg allowed companies to set up what were effectively brass plate operations in the country in order to avoid tax.

In Glanbia's case, it put more than €1bn into a company with no staff. That money was then loaned to Glanbia in Ireland.

The interest paid on the loan was used to reduce Glanbia's tax bill in Ireland while attracting no tax liability in Luxembourg.

In a statement this morning, Glanbia confirmed that it has group companies in Luxembourg, which are clearly identifiable as Glanbia companies and are part of "inter-group financing arrangements underpinning our international operations".

It said the group is fully tax compliant in all of the jurisdictions in which it operates and the majority of its 2013 corporate tax payments were made to the Exchequer.

Construction firm Sisk was among the other companies to have set up similar subsidiaries alongside multinationals such as Ikea, Pepsi and Amazon.

Details of the documents are published in The Irish Times having been shared by the Washington DC-based ICIJ.

There is no suggestion that there is anything illegal in the practice.

The leaked documents include hundreds of private tax rulings - known as comfort letters - that Luxembourg provides to corporations seeking favourable tax treatment.

Luxembourg officials denied any "sweetheart deals" in its tax system.

"The Luxembourg system of taxation is competitive - there is nothing unfair or unethical about it," ICIJ quoted Nicolas Mackel, chief executive of Luxembourg for Finance, as saying in an interview.

EU state aid regulators are investigating Amazon's tax deals with Luxembourg, saying the arrangements could have underestimated the US online retailer's profits and given it an unfair advantage.