Rishi Sunak has said Sir Keir Starmer should slash Britain’s soaring welfare bill in order to fund a vital increase in defence spending.

In his first sit-down interview since leaving Downing Street in July last year, the former Conservative Party leader warned the cost of sickness and ill-health benefits is growing “at a very rapid rate”.

Mr Sunak set out how Sir Keir could “save billions and billions and billions” from that budget, which could then be ploughed into defence spending in a rapidly uncertain and unsafe world.

Speaking to Nick Robinson for his Political Thinking podcast, Mr Sunak explained: “It’s important, as the Prime Minister’s done, that we raise defence spending but we will need to go further.

“That, I think, requires quite a radical restructuring of the state in order to provide security.”

Asked whether that means cutting other things we value in order to spend the extra defence cash, Mr Sunak said cutting the country’s welfare budget was “obvious and necessary”.

“We spend more on welfare benefits, sickness and ill-health, disability benefits, all that set of benefits than we do on defence spending today, and it’s been growing at a very rapid rate,” said the Tories‘ ex-leader.

“I think it is possible, because of the size of that budget and how much it’s increasing, that you can save billions and billions and billions from that budget, and quite frankly that is the most important thing for the country to do next so we can fund defence adequately.”

He described the current welfare system as “spiralling out of control” and “unsustainable”, with three times as many people today claiming they are not fit to work than a decade ago.

Mr Sunak claimed: “That tells me the system is not working as it was intended to, and actually I was brought up to believe that hard work is fundamental to how we support ourselves.”

“Helping more people into work is the moral thing to do.”

The former prime minister also insisted that Britain can still trust America as a defence and security partner, but insisted Europe must be much more responsible for its own military spending.

“We can’t expect America to bear any burden for our security if we are not prepared to make those sacrifices ourselves

“What has happened over the last few weeks has been clarifying, and we have just had to be open and honest about that now.”

He also described the showdown between Ukrainian president Volodymyr Zelensky and Donald Trump in the Oval Office last week as “wrong” and “very hard to watch”.

Mr Sunak told Nick Robinson: “It was very hard to watch, as someone who has spent a lot of time with Volodymyr, been in Kyiv with him, has seen what he has had to go through for his country.

“To see him be called a dictator, to be told that he started this war, to be treated that way was wrong.”

Nick Robinson’s interview with Rishi Sunak on the Political Thinking podcast is available on BBC Sounds.