Brown was chancellor of the exchequer for ten years, prompting speculation that he would be reluctant to relinquish control of the government coffers and undermine Darling’s authority by staying involved in Treasury matters.

But Darling said that he had worked with Brown for a number of years, and would not shy away from standing up to the PM if required. He said the new premier would expect nothing less from his chancellor.

‘You do have to say no. A chancellor that just says yes to him (Brown) on public spending would be no use to him. The ability to say no is essential to any chancellor.’

Darling said he was in constant touch with Brown and that, through the course of the 25 years that they had known each other, they had developed a relationship based on mutual respect.

‘The prime minister and the chancellor have to work well together. If there is an issue, we have to discuss it. We have a good working relationship and we want it to stay that way,’ Darling said.

Darling said that when he was serving as chief secretary to the Treasury (Brown’s deputy) after the 1997 general election landslide, he had been forced to tell his then boss that some spending was not possible.