Britain should start talking about rejoining the EU, according to a former senior civil servant who ran the Brexit department.

Philip Rycroft, who was permanent secretary of the Department for Exiting the EU, said the “argument was there to be won” about going back into Europe, adding that a “clear-headed appraisal of what is in the country’s best interests” was needed. However, he said rejoining the bloc could be a “long and windy” road.

“Most economic analysis suggests that we have taken a significant hit to GDP as a result of leaving the single market,” he wrote in the Times. “The precise number, and the impact on our export performance to the EU and beyond, might be subject to debate, but no one can credibly claim that we have marched to the sunny uplands of sustained economic growth as a consequence of Brexit.”

Rycroft said the promises of the Brexit campaign on issues from economics to immigration had not lived up to expectations. “The great promise of a comprehensive trade deal with the USA now seems like an impossible dream,” he said.