There is little prospect of Britain leaving the EU before 2020, according to the former head of the Civil service.
Speaking at a Scottish Parliament event, Lord Bob Kerslake said that leaving the EU would be “a lot more complex and take a lot more time than people think it will."
Lord Kersalke, who held the position for two years from 2012 to 2014, described Brexit as an "enormous challenge."
“I don’t believe we will have completed the process by 2019. I think there will still be big issues being resolved", Lord Kerslake said, according to the Daily Mail.
“I think it’s at least five years away, maybe longer. All this talk of it being a two-year process is optimistic."
Britain’s exit is governed by Article 50 of the Lisbon Treaty and when invoked this will set out a two-year process to leave the EU.
The news comes as Iain Duncan Smith has called for talks about Britain leaving the EU to take place “as soon as possible”.
Writing in a column for The Sun the prominent Leave campaigner said: “It is clear that the referendum was NOT a suggestion… We need to get on with triggering Article 50, as the Government has said, in early 2017.”
The leaders of Germany, France and Italy met to discuss the future of the EU and the implications of Britain triggering Article 50.
It is the second time the three largest eurozone countries have held talks since Britain voted to leave the EU in June.
The meeting comes ahead of an informal European Union summit to which the UK has not been invited.
