NINETY drivers with a private ambulance company are set to share in huge payouts after winning a marathon dispute with their bosses.

Union leaders said the jackpot will total hundreds of thousands of pounds, but The Sentinel understands it could rise to £1million.

A legal ruling against Parkwood will hand staff up to £2,000 each in compensation for having their wages and conditions wrongly pegged back for the past three years.

But it will also clear the way for other sums in back-pay currently being calculated.

National arbitration agency ACAS last night found the company, which ferries 600 patients a day to routine hospital appointments, breached agreements designed to protect workers transferred from the NHS.

The workforce, based at a depot on Burslem's Sneyd industrial estate, has been in dispute with the company since soon after Parkwood won the contract from the former Staffordshire Ambulance Service in 2006.

Drivers recruited after the changeover were put on significantly lower earnings, sick pay and holiday entitlement than colleagues who moved from the NHS.

The recruits now number about 50, but the Unison health union is pursuing a separate action against Parkwood over the other 40 who have not had a pay rise since they switched.

Drivers staged a work-to-rule in December 2007 in protest about the two-tier pay, but returned to normal to allow arbitration. The process was then delayed until this spring despite intervention from NHS lawyers and Government ministers.

Unison national leaders hailed the verdict as a victory which would set a precedent to stop other private contractors using the same tactics when awarded NHS work.

General secretary Dave Prentis, pictured, said: "We always maintained that Parkwood were not rewarding their staff in accordance with the Workforce Matters Code of Practice and the case's independent arbitrator has agreed.

"The total back pay for new starters and transferred staff probably adds up to several hundred thousand pounds. "

The University Hospital of North Staffordshire had procured the multi-million pound contract, which also involved the area's two primary care trusts and the Combined mental health trust.

Mr Prentis added: "It is worrying that the procurement team did not pick up on the terms and conditions at the start and realise that it was short by this huge amount."

Stoke-on-Trent North MP Joan Walley who liaised with the staff and ministers said: "I deplored the length of time it took to trigger the ACAS procedure. The code of practice is to ensure commissioners and contractors do not ride roughshod over guidance which exists to provide a level playing field."

The work has now been handed back to West Midlands ambulance trust despite a bid by Parkwood to keep it.

No-one from Parkwood was available for comment.