The UK’s competition watchdog has asked its counterparts in Brussels to hand over responsibility for investigating the £31 billion merger of O2 and Virgin Media.

The deal will only affect customers in the UK, and the effects of it will only be felt after the Brexit transition period ends, Competition and Markets Authority boss Andrea Coscelli argued.

Months after indicating it was interested in running the competition process for the deal, which sees Liberty and Telefonica, and their subsidiaries, combine forces, the CMA has formally asked Brussels for permission to take over.

“We’ve sent a formal request to the European Commission to review the proposed deal between Virgin and O2,” Mr Coscelli said on Thursday.

“Ultimately, this is a decision for the EC, but as the merger will only impact UK consumers – and any effects would only be felt after the end of the transition period – it is only right for the CMA to request it back.”

Normally when a deal only affects customers in one country, the domestic regulator takes charge of the investigation.

However, the size of the Liberty and Telefonica tie-up pushed it above the limit where Brussels is meant to take charge.

In July, months before it was formally notified of the plans for the two companies to merge, the CMA told the Financial Times that it wanted responsibility for the deal.

“This important merger will only impact consumers in the UK and since any review will likely conclude after the transition period, it is only right for the CMA to request it back now,” it said in a statement to the paper.

The European Commission now has until November 19 to decide whether to transfer jurisdiction to London.