Prime Minister Tony Blair was yesterday forced to defend his handling of the health service as he toured a hospital in Health Secretary Alan Milburn's Darlington constituency.

A report from the King's Fund health thinktank said the NHS had been ''overwhelmed'' by a flood of directives, targets and structural changes since Labour came to power, while the Government had failed to develop a ''coherent and principled'' approach to health.

Yesterday doctors and nurses at the Darlington Memorial Hospital told the Prime Minister how staff shortages were putting them under pressure.

Consultant urologist Simon Fulford, who welcomed Mr Blair to the hospital's new £460,000 endoscopy unit, said he was only there because he had been called in on his day off to cover for absent staff.

He told the Prime Minister: ''We always need more resources and more money. For instance, today I am not supposed to be here. Someone is on holiday so I have to come in.''

Mr Fulford later told reporters: ''It is a fairly common occurrence in the NHS these days if the junior staff are on holiday, people have to give up their free time to do extra sessions."

Ward sister Maggie Donaghue told Mr Blair: ''We have big problems at the moment with recruitment.

''We know you are doing a lot for us but it is the problem we have now. There are nurses training but we need the nurses now.''

King's Fund chief executive Rabbi Julia Neuberger said: ''The NHS is overwhelmed with well-meaning policy directives, must-do targets and structural changes. Primary care trusts in particular are struggling to meet all of the policy imperatives Labour has set them.''

Mr Blair said: ''From the Government's point of view it is important we make sure that any money that is being put into the health service is spent well. But there is tremendous reform and change going on in the health service.''

He said the Government was taking steps to prove to health workers that necessary reforms were being made.

The Department of Health described the report as ''interesting'' and said the process of setting up structures was bound to involve a great deal of change in a short space of time.