The Government cannot afford to delay essential reform of Britain's public services, David Cameron has warned.
As ministers prepared to publish legislation to radically overhaul the NHS, the Prime Minister said that failure to modernise was draining resources away from the public sector.
In a keynote speech at the Royal Society of Arts in London, he dismissed suggestions that services could carry on as they were as "a complete fiction".
The Government's plans for the NHS have been denounced by six health service unions - including the British Medical Association and the Royal College of Nursing - as "potentially disastrous". But Mr Cameron insisted that change was essential.
"Every year without modernisation the costs of our public services escalate. Demand rises, the chains of commands can grow, costs may go up, inefficiencies become more entrenched. Pretending that there is some 'easy option' of sticking with the status quo and hoping that a little bit of extra money will smooth over the challenges is a complete fiction," he said.
"We need modernisation, on both sides of the equation. Modernisation to do something about the demand for healthcare, which is about public health. And modernisation to make the supply of healthcare more efficient, which is about opening up the system, being competitive and cutting out waste and bureaucracy. Put another way: it's not that we can't afford to modernise; it's that we can't afford not to modernise."
The Prime Minister also rejected suggestions that the Government was trying to do "too much at once" in pushing through both health and education reforms.
"Every year we delay, every year without improving our schools is another year of children let down, another year our health outcomes lag behind the rest of Europe, another year that trust and confidence in law and order erodes," he said.
"These reforms aren't about theory or ideology - they are about people's lives. Your lives, the lives of the people you and I care most about - our children, our families and our friends.
"So I have to say to people: if not now, then when? We should not put this off any longer."