Negotiating Britain's withdrawal from the European Union would take "a very long time" and the country would be likely to walk away without any "great successes", a former Cabinet Secretary has warned.

Lord O'Donnell, who worked under four Prime Ministers and was the country's highest ranking civil servant, said that countries like France and Germany would not allow Britain to leave with a good deal because they would not want to play into the hands of anti-EU opponents in their forthcoming elections next year.

He also told BBC Radio 4's Today programme that it took Greenland three years to negotiate an exit from the trappings of the EU, indicating that it could take up to a decade for Britain.

"There was only one issue for Greenland and that was fish," he said. "In terms of population they have rather fewer people than were at Wembley last night and it took them three years.