Boris Johnson’s Brexit deal would leave the economy 3.5 per cent smaller in the long term than if Britain were to remain in the European Union, according to the National Institute of Economic and Social Research.

The think tank said that the uncertainty ushered in by the Brexit vote had hit GDP by 2.5 per cent. It said, however, that the country would be even worse off under the government’s deal since it would damage Britain’s smooth trading relationship with the bloc.

“Uncertainty would be lifted, but customs and regulatory barriers would hinder goods and services trade with the Continent, leaving all regions of the United Kingdom worse off than they would be if the UK stayed in the EU,” the institute said. The impact