The former work and pensions secretary Iain Duncan Smith has insisted that the government’s Brexit strategy is actually "very simple" and basically amounts to "leaving the European Union".

Duncan Smith was responding to the resignation of the UK's ambassador to the EU, Ivan Rogers. In his resignation letter, Sir Ivan urged British colleagues in Brussels to challenge "muddled thinking".

But appearing on the Today programme, Duncan Smith claimed that there was no such muddled thinking and that the government’s Brexit plan was clear. Asked if he knew what the government’s objective was, he replied:

"Yes, it’s very simple, we are leaving the European Union."

Duncan Smith was then interrupted by fellow studio guest Jonathan Powell, former chief of staff to Tony Blair, laughing at the simplicity of his answer.

But he ploughed on: "It’s absolutely clear. We are leaving the rule of European law. We are taking back control of our borders. And we will then look to make arrangements with European Union over what kind of trading system."

Sitting alongside Duncan Smith, Powell said the Brexit negotiations were doomed to fail if ministers were not prepared to have civil servants like Sir Ivan telling them where they were going wrong.

"The point is to have someone who will tell you frankly what the problems are, who will point out to you the elephant traps, who will say these are the things that could go wrong. Then you make your decision as a politician, and the civil servant will then implement it. He will not argue back at that stage, he will implement them, he said.

"But if you are not prepared to have the argument, if you are not prepared to have someone who will tell you what the problems are, you are going to end up in a disaster. And that’s what’s going to happen with these negotiations if they really go for a patsy.

"You won’t know what’s going to happen, you will live in a miasma, you being the prime minister, the ministers. If they do not have civil servants telling them honestly what the other Europeans think, not telling them honestly what is possible to negotiate, they’ll live in this fantasy land of what’s possible, they’ll live in a Daily Mail world of what could be achieved. And they will fail."