Keir Starmer has vowed to be bold and face down “loud opposition” to his planned public health measures and NHS reforms after a major inquiry found the health service was “in critical condition”.

The prime minister said he was prepared to take “controversial” action to fix the NHS and public health in England after the findings by the cancer surgeon and former minister Ara Darzi.

In a speech at the King’s Fund, Starmer said he intended to perform “major surgery not sticking plasters” on the NHS and take “much bolder” measures to prevent illness.

He said the NHS had to “reform or die” and it would take 10 years to implement the changes needed. “We need to have the courage to deliver long-term reform – major surgery not sticking plasters. We’ve got to face up to the challenges – ageing society, a higher burden of disease,” he said.

The Darzi report concluded that years of neglect by previous governments had left the NHS “in critical condition” and unable to give patients the timely care they needed amid an explosion in demand caused by an ageing, growing and increasingly sick population.

It said A&E was in “an awful state” and cited evidence from emergency doctors that long waits were likely to be causing an additional 14,000 deaths a year.

The prime minister said he was “absolutely convinced” that prevention had to be central to his government’s 10-year plan for the NHS, including tackling tooth decay, smoking and obesity. He said he was shocked to find out how many children were admitted to hospital to have rotting teeth removed.

“There’s diet, there’s healthy lifestyle, we are going to have to get into that space,” Starmer said. “I know some prevention measures will be controversial, but I’m prepared to be bold, even in the face of loud opposition. So no, some of our changes won’t be universally popular, we know that, but I will do the right thing for our NHS, our economy and our children.”

Asked whether he thought doctors’ unions would welcome productivity reforms to the NHS workforce, Starmer said he was willing to challenge anyone who was “an inhibitor of change”.

“I’ve said we’ll do this with the staff, and we will,” he said. “But I know from my old job running the Crown Prosecution Service that whenever you try to reform anything, there will be some people, I’m afraid, who will say”: ‘Oh, don’t do that, it’s better as it is, I wouldn’t do that, keep things as they are.’

“We have to take that attitude on. In my view, it’s an inhibitor of change. So whilst we say we will do it with people, and we will; we will do it together, and we will; I know in my heart of hearts we will meet pockets of people who will say: ‘Don’t do it, slow down, go over there not over there, leave things as they are.’

“We have to take that on, and we will take that on. That’s part and parcel of the change that we need to bring about,” Starmer said.

Speaking just over six weeks before the budget on 30 October, Starmer the NHS would receive “no more money without reform.

“Reform does not mean just putting more money in. Of course, even in difficult financial circumstances, a Labour government will always make the investment in the NHS that is needed, but we have to fix the plumbing before we turn on the taps,” he said.

“So, hear me when I say this: no more money without reform. I’m not prepared to see even more of your money spent on agency staff who cost £5,000 a shift, on appointment letters which arrive after the appointment, or on paying for people to be stuck in hospital just because they can’t get the care they need in the community.”

Starmer said long-delayed social care reforms would be part of the government’s 10-year plan but that any change had to be achievable.

He said he was committed to building the 40 new hospitals first promised by Boris Johnson in 2019, though he emphasised that the previous government’s plans were misleading and unrealistic. Rachel Reeves, the chancellor, announced a review of the scheme in July and said it could not be implemented by 2030.

Labour commissioned the 142-page report by Lord Darzi, who was a health minister under Gordon Brown, when it came to power in July.