Financial services businesses face the largest cost impact by sector from Brexit, according to a report from Marsh & McLennan consultancy Oliver Wyman and law firm Clifford Chance.

It says about 70% of costs from new trade barriers will be felt across five sectors, also including automotive, agriculture and food and drink, consumer goods, and chemicals and plastics.

“The largest absolute impact will come from financial services due to London’s role as Europe’s financial centre and the fact it will be hard to mitigate impacts in this sector.”

The effect on London may be equivalent to about 2.5% of the city’s gross value added, accounting for about 40% of the national impact.

A wide range of trading relationships between the EU and UK are still possible, making Brexit outcomes uncertain. The report looks at impacts from tariff and non-tariff barriers if the two sides revert to a World Trade Organisation relationship – a “no-deal” Brexit.

Annual direct costs are estimated at about £27 billion ($47.6 billion) for UK businesses and £31 billion ($54.7 billion) for EU companies after initial mitigation steps.