Whitehall must hire an extra 1,300 specialists to deliver the next phase of the Brexit process, the chief executive of the civil service has disclosed.

John Manzoni said the government still needed to bring in more civil servants to tackle the major challenge of preparing new infrastructure and border controls that will be required when the country quits the EU.

"Do we have the people we need for today? Yes. Do we have the people we need to build all this stuff in 18 months? The answer is no, and we’ve got to get them," he told the Public Accounts Committee on Monday.

The chief executive said the civil service had the right staff on board for the divorce process of Brexit, also known as phase one, but conceded that it was still looking for specialists who could run the "implementation phase."

"It's work in progress. We do not have all the people today that we need to build all the things we’ve got to do. You can't, by the way, just click your fingers and say I need 300 or so people, because you need to decide what you want to do...and then the needs become clear," he said.