Healthcare assistants at NHS Tayside are threatening to work to rule over the decision to promote some to a higher band than others.
Around 150 healthcare assistants, who provide support to nurses and other medical staff, will see their pay upgraded this week.
The pay rise could be as much as £2,000 a year in some cases and, for some workers, will be backdated to 2015.
But an email to staff said other claims will, if successful, only be backdated to when they were raised.
Some healthcare assistants will also remain on the lower band and some are claiming the disparities are creating a “horrible atmosphere” amongst staff.
One worker said: “This week around 150 people, band 2, spread across the whole of Ninewells and Royal Victoria Hospital have signed up to be upgraded to band 3 as of July 1.
“This means I will be doing the same job but for less money. Management will say these people will be working differently and working towards a training schedule to fulfill the band 3 job description.
“I am of the opinion I have been doing band 3 for years.
“There have been threats of working to rule and there is a horrible atmosphere on most wards.
“Those who have signed up have done nothing wrong and have been put in a weird place by a management team that have handled this in the best tradition of NHS Tayside.”
The worker added: “The trade unions seem to be in no hurry to confront this issue and expect you to act as normal until something is worked out.”
An NHS Tayside spokeswoman said: “NHS Tayside is currently working in partnership on a review of Healthcare Assistant roles.
“NHS Tayside originally received a number of grading claims from Unison on behalf of Agenda for Change Band 2 healthcare assistants who wish to be considered for a Band 3.
“A Short Life Working Group has been established involving trade union representatives and NHS Tayside’s human resources department, pay office and the nursing and midwifery directorate to take forward these claims.
“The review of the claims submitted is an ongoing process and one-to-one meetings with affected staff will continue to be held over the coming weeks.
“In line with employment practice, re-grading requests will be effective from the date they were formally raised.”