The National Health Service is facing a "very challenging" year ahead, Tony Blair warned yesterday.

At his monthly Downing Street press conference, the Prime Minister insisted there had been "significant improvements" in the NHS since Labour came to power in 1997.

But he acknowledged that there were also difficulties as the service entered the next phase of the NHS ten-year plan launched in 2000.

"Whatever the challenge - and the next year will be very challenging for the reasons that we know - there have been marked, significant improvements," he said.

Mr Blair said: "No one is pretending that the NHS is without real challenges and problems. Of course it is, as every healthcare system in the world is."

But he called for a "sense of balance" which acknowledged improvements that had been made since 1997.

He said: "Yes, there are problems, but there have been major, fundamental and lasting improvements in patient care over these past few years."

Mr Blair also asked for recognition that reforms would "of course mean difficult decisions for the NHS".

"But the reforms will make the extra money that has gone into the NHS work better for the patients.

"I believe that in terms of things like waiting, the waiting times and waiting lists are the best the health service has had," he said. "The treatment for cardiac care or cancer care is the best the health service has had. The treatment in accident and emergency is transformed from what it was a few years ago."

Mr Blair stood by Health Secretary Patricia Hewitt who has come under fire from nursing and union leaders over the weekend.

Asked whether she was the right person to see through reforms to the health service, he said: "Absolutely, because she's the person who's taking through a difficult change programme and standing up for what is right."

The Prime Minister also backed Ms Hewitt's comments that the NHS had had its "best ever year".

He said: "She didn't just say this. "She said it because waiting lists have never been lower since the health service records began, accident and emergency improvement has dramatically improved in the last few years, cancer and cardiac care are the best they've been in the NHS, and we have record numbers of extra doctors and nurses. These are facts.

"And what is more the NHS building stock when we came to power, more of the stock was built (before) the founding of the NHS than after it - that's changed.

"That's why she said what she said."