The Resolution Foundation and the LSE said leaving the EU has reduced how open and competitive Britain’s economy is.

The UK has not seen a large relative decline in its exports to the EU that many predicted, although imports from the EU have fallen more swiftly than those from the rest of the world, the study suggested.

Less competitive

The full effect of the Trade and Cooperation Agreement will take years to be felt but the move towards a more closed economy, say the authors, will make the UK less competitive, which will reduce productivity and real wages, it was predicted.

The research estimated that labour productivity will be reduced by 1.3 per cent by the end of the decade by the changes in trading rules alone, contributing to weaker wage growth, with real pay set to be £470 per worker lower each year, on average, than it would otherwise have been.

Output of our fishing industry is expected to decline by 30 per cent and some workers will face “painful adjustments”, said the foundation.

The report added that the North East is expected to be hit hardest by Brexit as its firms are particularly reliant on exports to the EU.

Sophie Hale, principal economist at the Resolution Foundation, said: “Brexit represents the biggest change to Britain’s economic relationship with the rest of the world in half a century.

“This has led many to predict that it would cause a particularly big fall in exports to the EU, and fundamentally reshape Britain’s economy towards more manufacturing.

“The first of these has not come to pass, and the second looks unlikely to do so. Instead, Brexit has had a more diffuse impact by reducing the UK’s competitiveness and openness to trade with a wider range of countries. This will ultimately reduce productivity, and workers’ real wages too.

Hilary Benn, Labour MP and co-convenor of the UK Trade and Business Commission, said: “The Government’s Brexit deal is making businesses and consumers poorer at a time when people up and down the country are struggling to make ends meet.