UNIONS last night launched an attack on management at bus firm Stagecoach amid fears that a "nasty and bitter" pay dispute could cripple local services.

The Transport and General Workers Union said it had made no progress in its efforts to resolve a row over pay involving 600 workers at depots in Darlington, Hartlepool and Stockton.

Staff want a proposed 50p increase, bringing their pay up to £7 an hour, in line with bus drivers at rival Arriva, to be made immediately.

But Stagecoach is understood to have offered a 20p increase on an agreement being reached, followed by a staggered 30p increase in November.

Last night, Allan Gray, regional industrial organiser with the TGWU, said the first strike ballot papers were being sent out to its members on June 27. "All we have encountered from management is intransigence and all avenues look as if they will lead to a nasty and bitter dispute."

Stagecoach yesterday said it would be making no comment, but planned to issue a statement on Monday.