Gordon Brown will face an early test of his relationship with trade unions because of a series of disputes brewing in the public sector.

Despite generally positive links with union leaders, Mr Brown has come under fire in recent months over health workers' pay, civil service jobs and controversial schemes such as the private finance initiative (PFI).

Tony Woodley, joint leader of Britain's newest, and biggest, trade union, Unite, has made it clear he wants to see a change of policy and direction when Tony Blair is replaced.

Labour was "struggling" under Mr Blair's leadership and party activists had stopped being active, said Mr Woodley.

"It cannot just be down to the legacy of Iraq. We need a change of direction and policy and we need a leader who will listen a little bit more to some of the helpful comments we make."

Union leaders believe Mr Brown will receive strong backing from rank and file union members, many of whom are angry at Mr Blair for his foreign policies, especially Iraq, as well as his reforms to public services.

Despite huge investment in the NHS, unions are threatening national industrial action for the first time in a row over health workers' pay.

Mr Brown is blamed by many for the Government's decision to stage a 2.5% pay rise, reducing the value of the award to 1.9%.

Local government unions are also gearing up for industrial campaigns over pay and tackling inequalities between the earnings of men and women.

The current Chancellor has been heavily criticised by civil service union leaders for announcing 100,000 job cuts in government departments and agencies, a decision which has sparked a series of strikes.

Although the civil service unions are not affiliated to Labour, they will still be able to cause a few headaches for Mr Brown in his early days as Prime Minister.

Many union officials are waiting for changes in substance rather than a difference in style between the two men.

Mr Brown is a member of the Transport and General Workers Union, now called Unite after a merger with Amicus, and is seen to have a more sympathetic approach to unions than Mr Blair.

"He speaks our language and is able to deliver messages that we understand," said one trade union leader. "His record as Chancellor of redistributing wealth through initiatives like tax credits have really made a difference.

"Gordon is sometimes uncomfortable on the social stage, but he is always very comfortable when he is among trade unionists."