More than 20,000 Birmingham City Council workers have been ordered out on strike next week at the start of an escalating campaign of industrial action against a controversial pay and grading review.

Five unions voted for the one-day stoppage on February 5 - to coincide with a meeting of the full city council.

The action could close schools, leisure centres and crematoria. Dustbins may not be emptied, streets could go uncleaned and road repairs may be suspended.

But a joint statement by the unions - Unite, Unison, Amicus, GMB and UCATT - promising widespread disruption was being questioned last night after it emerged that only 4,462 out of 40,000 workers affected by the pay shake-up had actually voted to strike.

Although up to 70 per cent of those taking part in the ballots supported industrial action, a little under a quarter of union members entitled to vote actually did so.

Unison, the largest council union with 12,463 members, could only persuade 4,443 to take part in the ballot - with 2,610 voting to strike.

Leaders of the council's Conservative-Liberal Democrat coalition face the challenge of fighting their way through picket lines to get into the monthly council meeting, with hundreds of workers expected to ring the Council House in Victoria Square.

Yesterday's announcement marks a new and uncertain stage in a year-long campaign against the Single Status pay and grading review, which will see 5,740 employees suffer wage cuts - a few by more than £20,000 a year.

Thousands of blue collar workers, chiefly in the transportation and street cleaning departments, stand to lose lucrative weekly bonuses, and in some cases will be £10,000 a year out of pocket.

The Single Status reforms, which are supposed to iron out pay inequalities between men and women will see 81 council workers suffer wage cuts of more than £16,000 a year.

However, 41 per cent of staff get a pay rise while 45 per cent will still receive their existing salary.

Alan Rudge, the cabinet member for human resources and equalities, said he was disappointed at the "knee jerk" reaction by the unions. The threat of strike action would alarm the public and harm services, he said.

Coun Rudge (Con Sutton Vesey) added: "The vast majority of our employees do not want to strike. They want to resolve matters amicably.

Coun Rudge added: "Far from saving the council money, we have already spent more the £100 million in back-pay and our pay bill has risen by more than £23 million in this current year, rising to £29 million in the following year. And not one penny of this has been funded by central government, which has imposed this review upon us."

He will hold talks with the unions today and tomorrow in an attempt to halt next week's strike.

Union sources were making it clear that the strike will be the start of a campaign designed to force the council to abandon the pay and grading review. Tony Rabiotti, from Unison, said: "No one will be put in danger and essential services will be maintained."

The prospect of lengthy industrial action at Britain's largest local authority, with an impact on services, is likely to alarm the council leadership, which has informed 40,000 staff that they must abide by new contracts from April 1.

It was confirmed last night that 20,000 workers have already signed their new contracts.

The council employs almost 60,000 employees, but only 40,000 are involved in the pay and grading review.

Union leaders heaped criticism on the council. Unison regional secretary Valerie Broom said: "The result of today's ballot shows just how angry and frustrated Unison members in Birmingham are. Taking strike action is always the last resort, but the decision to impose grossly unfair new contracts has come as a hammer blow to staff and their families."

Joe Morgan, regional secretary of the GMB union, added: "The council's actions are outrageous. "It is not too late for the council to withdraw these proposals."

Steve Murphy, UCATT Midland regional secretary, said: "My members are being forced to reluctantly take industrial action, due to the appalling manner in which they are treated by their bosses."

Sir Albert Bore, leader of the council opposition Labour group, said he would support the workforce.

Sir Albert (Lab Ladywood) said staff had "no option" but to strike because their concerns about the unfairness of the new pay system were not being addressed by the cabinet.

He added: "There is total bewilderment as to how we have ended up with a pay and grading review in which there are so many losers. I believe there are basic flaws in what the council has been doing."