Question to the HM Treasury:

To ask His Majesty's Government what recent estimate they have made of the impact of Brexit on the economy.

The Office for Budget Responsibility (OBR) is the Government’s official forecaster.

In 2020, the OBR estimated that the additional trade barriers associated with leaving the EU will reduce trade intensity by 15 per cent and as a result GDP will be 4 per cent lower than it otherwise would have been. The OBR estimated that around two-fifths of the 4 per cent impact had already occurred by the time the EU-UK Trade and Cooperation Agreement came into force, that GDP would be 2.7 per cent lower by 2025, with the remaining reduction occurring by 2031.

In the OBR’s March 2024 Economic and Fiscal Outlook, they reaffirmed these assumptions were on track, and as of Spring 2025 these forecasts were unchanged.

Other independent studies are also consistent with this analysis, for example the National Institute of Economic and Social Research estimates that GDP will be 5 to 6 per cent lower as a result of Brexit.