Union leaders said walkouts may spread to Sheffield after a straw poll revealed 90 per cent support among workers, and proposed pay cuts have prompted similar unrest in Bradford.

The GMB union, which represents binmen in Leeds, Sheffield and Bradford, told the Yorkshire Post efforts were ongoing to avoid the type of action which is gripping Leeds.

But they made it clear workers would be balloted for strike action if negotiations failed, leaving two more councils facing the prospect of rubbish piling up in the streets for weeks.

The GMB said Bradford Council had told binmen it wanted to make savings which could see some workers lose £5,000 a year, a pay cut comparable to that faced in Leeds.

Regional union spokesman Steve Morris said yesterday: "Employees in Bradford were served with 90-day notices about changes to their bonus schemes and pay 29 days ago.

"Refuse staff are looking at losing a similar amount of money to those in Leeds which is more than £5,000. We had talks this morning with council officers which seemed fairly positive. But things may change. We had already had several meetings and we will have two meetings a week going forward. We have not drawn a line in the sand yet, but you never know."

In Sheffield, a row has broken out after it emerged that private contractor Veolia, which employs the city's 180 binmen, had different rates of pay for workers carrying out the same duties.

The GMB's Sheffield officer, Peter Davies, said: "It is a different issue in Sheffield compared to that faced in Leeds and Bradford. We have a dispute over the pay scales in place at Veolia.

"People working for the company can be doing exactly the same job as each other but get paid very different amounts and we are at the final stage of the dispute resolution procedure.

"We carried out a straw poll ballot of around 70 per cent of the workforce involved and 90 per cent of those people said they would consider taking industrial action over the issue.

"I will be meeting with management at Veolia early this month, and Acas ( the employment mediation service) have already been involved in talks. If we cannot reach some kind of agreement we will ballot for action at the end of October."

Veolia took over refuse collections in Sheffield in August 2001 and have a 35-year contract with the council which includes waste collection, recycling and running the city's incinerator.

In West Yorkshire, rubbish collections are still carried out in-house by both Bradford and Leeds Councils although local authority leaders in Leeds have said they were considering outsourcing the service.

Earlier this week, the Lib Dem leader of Leeds Council Richard Brett branded the city's bin collection service "very inefficient" and accused unions of making "highly misleading" statements about the pay dispute.

As the strike entered its fourth week on Monday, Coun Brett said wages would not change until January 2011 because of "pay protection" clauses and pleaded with strikers to return to work so talks could continue.

Refuse workers are among several categories of local authority workers facing changes in their salaries, and other unions, including Unite and Unison are also involved.

Council leaders in Sheffield were supposed to send out letters to employees on Friday about their pay and grading review but postponed the move until tomorrow over "technical issues".

Becky Hellard, Bradford Council's strategic director of corporate services, said last night: "We are proposing to offer new contracts to approximately 600 employees.

"The proposed changes are being made to conform with Single Status, a national agreement reached between unions and employers which councils everywhere must implement.

"We have been working with the trade unions and negotiations are progressing well."