Retaining a customs union with the EU after Brexit will cause the British economy to lose around three percent of its value in the long term. This is the most favorable option being considered by the opposition Labour Party.

Instead of staying with the EU, leaving in such a way would cause a loss equivalent to about 800 pounds per person per year, 10 years after Brexit. This data is from a report put out by National Institute for Economic and Social Welfare (NIESR).

A customs union arrangement with the EU will make trade a costlier proposition for the UK and limit the country’s ability to strike free trade deals with other nations. Britain’s GDP could come down by as much as 3.1 percent 10 years after leaving the EU in such a scenario, while tax revenues could come down by 2.9 percent.

While Brexit supporters feel that the customs union arrangement with the EU will give Britain greater freedom in signing trade deals with other nations, it could also lead to a reduction in access to EU markets.