Former Conservative leader Sir Iain Duncan Smith has said Dominic Cummings aimed “to do as much damage to Boris Johnson as possible” when delivering evidence. 

Sir Iain said it should have been the former aide’s job to ensure that Mr Johnson’s “rather complicated life” was managed and that the Prime Minister was focused on battling the pandemic.

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Cummings delivered testimony to a cross-party committee about the handling of the Covid-19 pandemic and painted a picture of the chaos in No 10.

Speaking to BBC Radio 4’s Week In Westminster, Sir Iain, who had his own bitter falling out with Mr Cummings as Tory leader, said: “We all have to handle things and crises that happen within families, even while we are running things.

“The idea that somehow these were peculiar to the Prime Minister – maybe in the extent of them, and maybe in a rather complicated life sometimes – but that still doesn’t mean you can’t focus.”

“He was finalising his divorce, his girlfriend wanted to announce being pregnant, an engagement… certainly he had a very difficult time mid-February in his private life for sure.”

In response to the suggestion that Mr Cummings was claiming the Prime Minister was not focusing on the issue, Sir Iain said: “Well, maybe, but what is the role of Dominic Cummings as his main political adviser?

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“To structure things around him so that the key moments are dealt with in a structured way, allowing him to focus on the requirements and the decisions that are needed.”

Sir Iain said Mr Cummings’ goal was “to do as much damage to Boris Johnson as possible”.

Sir Iain Duncan SmithSir Iain Duncan Smith (UK Parliament/Jessica Taylor/PA)

He suggested it was inevitable that the relationship with Mr Cummings would result in a row “because this goes to the heart of his character”.

While Mr Cummings was intelligent, has good ideas, and is a disrupter, “managing the arguments and bringing people with you” were what was required in running a government “and of course, this was not what he really does”.

“And therefore his frustration and his anger that everybody else’s belief is stupid – as with me, as with Boris Johnson – nobody is good enough to understand what he really wants, and therefore they are to blame for it.”

Sir Iain added that a prime minister was often only as good as the “structure and the people” around them.

“I always thought that that appointment (of Mr Cummings) was, personally, going to end somewhere along this road.