Health Secretary Andrew Lansley today said there was "risk" involved with his radical NHS reforms, but change was necessary to improve standards for patients.
There would be a "greater risk" if the health service was not shaken up, Mr Lansley said.
Under the Health and Social Care Bill, most of the NHS budget will pass to GPs who will take control of commissioning services for patients. Strategic health authorities and primary care trusts (PCTs), which currently commission services, will be abolished.
The plans were denounced earlier this month by six health service unions - including the British Medical Association and the Royal College of Nursing - as "potentially disastrous".
Speaking to BBC1's Andrew Marr Show, the Health Secretary said: "I didn't say there wasn't risk. Of course there's risk because there's change.
"But actually if we don't change, the greater risk is that these problems that we have at the moment that we have to deal with won't be solved."
The NHS budget would be increased by £10.7 billion over the next four years but spending alone was "not the answer", Mr Lansley said.
"We discovered under Labour spending money isn't the answer, we have to deliver the results for patients. We don't get the results we should compared with other European countries; if we did, we would save thousands of lives."
The reforms would result in a redundancy bill of £1 billion, he said, but savings would reach £5 billion over the course of this parliament and around half of PCT staff would continue to be employed.
Defending the sweeping changes, Mr Lansley said: "How many patients have actually been treated directly by a Primary Care Trust?
"I'll tell you what actually runs the system - General Practice already makes most of the decisions about the care of patients in the community and their referrals and prescribing.
"Hospitals provide most of the secondary care and tertiary care to patients - I'm not interfering with them. I'm giving them greater freedom on both sides of that equation."
Mr Lansley said he did not necessarily want to see more private involvement in the NHS and such decisions would be up to patients.
"What I want to see is the best providers, whoever they may be," he said.
"You see, when Labour gave the private sector a chance to provide additional capacity, they rigged the market for them.
"They said: 'We're going to guarantee you're going to get paid whether or not the patients choose to go to you and we're going to pay you 11% more than the NHS price'.
"They stopped NHS foundation trusts bidding for that capacity. I actually do believe in competition."
So far, 141 GP consortia, serving more than half of the population of England, have now signed up as "pathfinders" to pilot the new arrangements ahead of their planned implementation in 2013.
A YouGov survey commissioned by public services union Unison found today that only 27% of people are behind proposals to let profit-making companies increase their role in the NHS.
Half of the 1,892 respondents opposed the policy, with hostility most evident among Lib Dem voters, where 56% were against, and just 30% in favour.
The use of private companies was supported by 46% of Conservative supporters who took part in the poll, while 32% were against the initiative.
Shadow health secretary John Healey said the NHS did need reform and improvement but the Government's shake-up was not the answer.
He told Sky News' Murnaghan programme: "Exactly the wrong thing to be doing in the view of many - including the Health Select Committee which is led by the Conservatives - is to launch this huge internal reorganisation, a waste of perhaps of £3 billion which should be spent on patient care.
"It's going to make it harder, not easier, to meet the real challenges of the health service and they include moving more services out of hospitals and closer within patients' reach and in the community.
"Those are big changes which could become much more difficult under the new system."