Unions representing drivers, maintenance staff and London Underground workers are due to announce the result of several ballots in separate disputes over pay, working conditions and privatisation.

The first result is expected on Wednesday, when the Rail Maritime and Transport union is due to reveal whether thousands of London tube workers support action in a dispute over job protection and conditions of service in the event of parts of the system being privatised.

The union could set dates for strikes which would badly disrupt the London Underground network.

The RMT will also announce results later this week from ballots of railway maintenance workers employed by six private companies in a dispute over pay and hours.

Last week, employees at seven out of eight maintenance companies whose ballot results were announced voted for strike action by margins of up to five to one.

Union chiefs plan action

A consultative meeting of local officials will be held next weekend on what form of industrial action to take, and the union's executive is set to decide its next move the following week.

In a separate development, RMT leaders cancelled a ballot of 4,000 Railtrack workers - mostly signalling staff - after an improved pay offer from the company.

The new offer means staff would get an increase of £10 per week or 4.5%, whichever is the greater. Railtrack also improved its offer for 1999 to the Retail Price Index rate plus 1%.