The UK’s Competitions and Markets Authority (CMA) may require significant reform and investment after the UK leaves the European Union, according to top London lawyers.

Christopher Bright, who practices UK and EU law at Shearman & Sterling, said big merger deals may in future have to go through the CMA, which will stretch its resources.

Mergers would have to be separately reviewed by the CMA rather than the European Commission, unless the UK decided, like Norway, to allow the Commission to adjudicate on its cases.

Margrethe Vestager has been the European competition commissioner since 2014.

Mr Bright said much of the CMA’s current work “focuses around market investigations in the domestic economy” and “taking on a role in major cases will require the agency to be reformed to deal efficiently and effectively with the workload”.

If the UK joined the European Economic Area (EEA) after Brexit, an idea floated in some quarters, then EU competition rules would continue to apply in the UK.

Alex Nourry, head of the antitrust practice at “magic circle” firm Clifford Chance, said the implications of Brexit for competition law would depend on the outcome of UK-EU negotiations.

However, he added: “It is likely that EU competition law would cease to apply in the UK, and that UK courts and competition authorities would cease to be bound by EU case law and decisions, creating scope for divergence over time.”