Freight entering the UK will clog up key ports should the country adopt a similar status to Norway upon completing its withdrawal from the European Union.

The warning, published in The Guardian newspaper, came alongside a prediction of a 4.5% fall in gross domestic product by 2030 should Brexit leave the nation outside the customs union.

Jonathan Roberts, head of communications at the UK Chamber of Shipping, said £120bn worth of goods is transported through Dover alone every year.

“The