Hundreds of hospital workers in Glasgow have staged an unofficial walk-out over pay.

An estimated 400 administrators and clerks at four hospitals in the city took the action on Thursday following a dispute which centres on job regrading.

It is thought that a similar number could join the strike on Friday.

This apparent disregard for the welfare of our patients is unacceptable

Dr Bill Anderson Medical director

About 100 striking workers gathered outside Glasgow Royal Infirmary on Friday morning to demonstrate.

The action was attacked by Health Minister Malcolm Chisholm, who told BBC Scotland: "I would urge them to return to work and condemn their action.

"It is unofficial action. I want them to return to work, their union wants them to return to work and patients want them to return to work."

Unison urged its members taking part in the strike to return to work so negotiations could begin.

Walked out

Joe Di Paola, Unison's Scottish organiser, said: "Unison simply doesn't understand why this action is being taken now instead of waiting for a Scottish-wide offer on low pay to be made next week.

"It is doubly perplexing given the procedure for the branch to get a ballot for official action has already started."

North Glasgow University Hospitals NHS Trust described the action as "irresponsible".

Medical director Dr Bill Anderson said: "These staff play a crucial role within the health service, providing administrative support in our wards and clinics.

"Their absence will have an immediate and harmful effect on patient care.

"This apparent disregard for the welfare of our patients is unacceptable."

Workers are unhappy over pay

The trust said it believed the talks over regrading had been making good progress.

"We are asking the staff to consider their responsibilities to patients, to end this illegal action and return to work immediately," added Dr Anderson.

However, it is understood that workers plan to continue their action until at least Monday.

The strike initially affected Glasgow Royal Infirmary, the Royal Maternity Hospital, Stobhill Hospital and Canniesburn Hospital.

About 400 clerks and administrators walked out on Thursday afternoon.

It was thought that a further 400 workers at facilities including Gartnavel General Hospital, Western Infirmary and Glasgow Dental Hospital could join the strike on Friday.

Proper procedures

Talks over regrading have been taking place between health union Unison and North Glasgow NHS Trust since January.

A source close to the striking workers said a formal request to ballot for strike action was made three weeks ago but turned down by a senior Unison official.

One Royal Infirmary employee said on Friday that there was a great strength of feeling.

"We have been in negotiations for 10 months with the trust for regrading," he said.

"They have now withdrawn their offer and backed us into a corner.

Stobhill Hospital has been affected by the strike

"We have nowhere to go. The union isn't officially backing us for anything."

Unison is encouraging staff to return to work and use the proper procedures to deal with their grievance.

It is feared that a strike by hospital clerks and administrators could seriously disrupt admissions, theatre schedules and clinics.

Three hundred ancillary staff at Glasgow's Royal Infirmary staged strike action earlier this year over pay.

The dispute was resolved after Sodexho, the private company providing cleaning services to the hospital, agreed to pay the workers �5 an hour.

Staff in turn agreed new arrangements for overtime and shift work.