The health secretary, Patricia Hewitt, today insisted that NHS values were "non-negotiable "as she defended privatisation to improve the NHS in the 21st century.

Speaking in a lunchtime fringe party conference debate organised by the NHS Confederation on the future of the national health service, Ms Hewitt attacked critics who insisted the government's reform agenda was undermining its values.

A trinity of factors - an ageing population, rising patient expectation and medical and technological advances - made the need for further reforms necessary, Ms Hewitt said as she gave a robust defence of the use of markets to drive improvements.

"The founding values of the NHS are non-negotiable - free at the point of need and available to everyone," Ms Hewitt told delegates.

"We are looking for the best way to ensure we safeguard these values in times that are changing faster and faster than most of us imagined 10 years ago.

"So the values do not change but what does change is the application of those values, the structures and the way we work ... we cannot run a 21st century healthcare service on structures from the 1940s."

Ms Hewitt said the "ideological" preferences of healthcare workers who believed services should be solely delivered by the public sector should be secondary to the needs of patients.

Ms Hewitt argued that the NHS had always had a "mixed economy" approach.

General practitioners had traditionally been self-employed business people whose salaries were drawn from the profits made from their practice, Ms Hewitt said.

Greater use of the private and voluntary sector would ensure patients were best served. "We need an element of competition because if services in a particular area are not good enough, then doesn't it make sense to go and out and see who can give the best services to the communities?"

Ms Hewitt cited the decision by the local PCT in Barking to bring in a private GP provider because there were not enough GPs to do the job.

But while the NHS should continue to provide services, these did not necessarily have to be "state owned" and answerable to Whitehall.

Ms Hewitt cited the foundation trust policy - once deemed controversial - that gave local people ownership of their NHS organisations.

"Foundation trusts are I think one of the best guarantees that the NHS will continue to be a provider and not just a commissioner of care and indeed a provider of the majority of hospital services," she said.

Ms Hewitt acknowledged that some changes currently under way were "difficult", especially in light of the financial problems facing the NHS.

But she said that far from causing the financial deficits, the reform of the NHS financing system had helped to uncover the scale of the problem.

Ms Hewitt reiterated her view, which rankled so much with healthcare unions earlier this year, that the NHS was growing from strength to strength.

"The NHS is already bigger and better than it was 10 years ago and we will continue to improve, indeed transform, the quality of care it can offer dramatically in years to come."