Three Ireland has formally completed its €780m acquisition of rival network O2 Ireland, more than a year after the deal was first announced.

The takeover gained approval from the European Commission in May and makes the combined network the second largest mobile operator in the country, with a market share of around 40%.

Next year both UPC and Carphone Warehouse will launch mobile services on the Three network, which was one of the conditions of Commission’s approval.

Despite this there has still been some concern about the impact the deal will have on competition in the market.

In a notice on the European Commission's approval, regulator ComReg said that competition issues "will not be fully addressed” by the measures agreed, and that “negative consequences for Irish consumer welfare may result” from the deal.

In a statement welcoming the formal completion of the deal, Three CEO Robert Finnegan said they would now “get down to the task of combining the strengths and talents” of the two firms.