Public sector workers will today challenge Tony Blair's plans to use private cash to improve public services.

Union leaders will question the Prime Minister's flagship programme for Labour's second term in a meeting tonight.

Mr Blair has invited union officials to Downing Street in a bid to ease fears about his plans for increased private sector involvement in schools and hospitals.

Dave Prentis, general secretary of Britain's biggest union, Unison, said: "We will challenge the notion that the private sector equates to efficiency and effectiveness.

"We challenge the idea that there is a wealth of private sector managerial experience ready and able to turn round our public services.

"This is simply not true."

The Government has not detailed its plans, but they are thought to include more private finance initiatives (PFI).

But Mr Prentis said claims PFI represents value for money "beggared belief".

Mr Blair's official spokesman said: "We are absolutely committed to getting in the extra investment into our public services.

"We are adamant that to get the most out of that investment it has to be accompanied by reform.

"Part of that, but only part of that reform process, is the greater use of the private sector where we can improve services for pupils, for patients, for passengers."