Security group Reliance looks set to lose its contract to transport prisoners in Scotland after the Scottish Prison Service announced it planned to transfer the service to a rival firm.

The SPS said it intended to award the contract for court custody and prisoner escort services to G4S Care and Justice Services (UK) Ltd, formerly known as Group 4 Securicor.

The SPS must allow a 10-day cooling-off period under European procurement regulations before finalising the contract to allow any bidder to make representations.

A spokesman for the service said the decision had been the outcome of a routine competitive tendering process.

Reliance Secure Task Management has been transporting prisoners in Scotland since it was awarded the £126m SPS contract in November 2003. The current deal, which involves the transfer of 180,000 prisoners annually, is due to expire next January.

Reliance has been plagued by prisoner escapes during its seven-year tenure, including one incident in which a prisoner climbed out through the roof of a van while being taken to Glasgow Sheriff Court.

Last April a prisoner serving seven years for serious assault fled from a van after kicking open the door, which was unlocked, while the vehicle was sitting at traffic lights.

In October 2009 Sheriff Ian Abercrombie blasted the service after a prisoner who was due to appear for trial at Inverness Sheriff Court was taken to Aberdeen instead.

Grant Adams, head of operations for Reliance in Scotland, apologised in person to the sheriff after being ordered to appear in his courtroom at 10am the following day. He blamed a "significant error" in the booking process for the delay.

G4S is the largest security firm in the UK and Ireland, employing 40,000 people and with an annual turnover of £1 billion. It currently transfers prisoners to and from 175 courts around Britain.

Russell Hobbs, Managing Director of G4S Court Services, said: “We are delighted to be providing court services for Scotland and look forward to working with the Scottish Prison Service.”

"G4S has unrivalled expertise in the care and transport of prisoners, and we were the first private company to take over court services from the public sector in England and Wales in 1993."