The European Commission (EC) has told Ireland it believes it gave illegal state aid to Apple. In a letter published today and originally sent to the country in June, the EC is accusing Irland of helping the computer giant through special tax arrangements. The European Union has accused Ireland of giving Apple illegal state aid through tax arrangements, which helped the iPhone maker shelter tens of billions of dollars in international revenues from tax.

In the letter, European Competition Commissioner Joaquin Almunia told the Dublin government that tax deals agreed in 1991 and 2007 appeared, in his preliminary view, to amount to state aid that broke EU laws and could be clawed back from the U.S. company.

"The Commission is of the opinion that through those rulings the Irish authorities confer an advantage on Apple," Almunia wrote to Ireland in the letter, which was dated June 11.

The Irish government and Apple have long denied any deals were agreed.

Ireland's corporate tax rate is set at 12.5%, but Apple enjoys an effective rate of tax of 2%, due to the way it channels overseas sales through its subsidiaries.