Ireland may never see the full €13bn (£10.8bn) in unpaid taxes owed by Apple, the European commission has said, if other EU countries go after the American tech giant for a share.

The EU executive also said Apple could reduce its multibillion-euro tax bill to Ireland if it increased payments to its US parent company, as it revealed the full text of its landmark ruling against the US tech giant for the first time.

Margrethe Vestager, the EU competition commissioner, suggested Ireland may not see the full €13bn in back taxes if Apple chose to pay larger amounts to its US headquarters to fund research and development.

Speaking to the Irish Independent, she said the total paid to Ireland could be reduced because other EU member states may demand more tax from Apple if they concluded that the US tech firm had underpaid them, because it had been routing profits to Apple’s Irish headquarters in Cork.

The full text of the EU’s decision, published on Monday, sets the stage for a titanic legal battle, which pits the European commission against Apple and Dublin, with implications for hundreds of companies.

In August, the commission said a sweetheart deal devised by the Irish government had allowed Apple to pay tax of just 0.005% in 2014 and an average rate of 1% over many years.

Speaking on Monday, Vestager said the full amount may not be payable to Ireland.

Apple created two companies in Ireland, Apple Sales International and Apple Operations Europe, as it went on a journey to become the biggest profit-making firm in the world.

“The amount to be paid back to Ireland would also be reduced if the two companies were required to pay larger amounts of money to their US parent company to fund the research and development efforts,” Vestager said.