TRAM workers could be balloted for industrial action over new rosters which they say means an increase in weekend working for no extra pay.
Tram drivers and ticketing staff are angry over the changes which come just ahead of the festive season, as well as plans to run all-night trams at Hogmanay for the first time.
The dispute also comes just weeks ahead of the opening of the new Edinburgh Gateway tram-train interchange.
The Unite union accused management of failing to listen to their employees’ concerns and said the action could involve more than 100 drivers and ticketing staff.
Unite deputy Scottish secretary Mary Alexander said: “Our members are deeply unhappy about the changes in rota that Edinburgh Trams is trying to force on them.
“We will be meeting with our shop stewards later this week and discussing how to take this matter forward.
“If the management of Edinburgh Trams don’t start listening to our members’ concerns, we may be left with no option but to carry out a consultative ballot for industrial action.”
Trams management say the changes are intended to prepare the service for expansion to meet demand.
But one employee said: “Staff have had enough of empty promises and the way that they are treated by the company.
“A new roster is being introduced in four weeks’ time and staff have not been advised what they are working over the festive period.
“The roster has increased weekend working with only 15 Saturdays or Sundays off in a year. Working hours have increased along with reduced break times.
“Work/life balance has been reduced and working unsociable hours has also increased to during the night with no alteration to wages.”
He said the company was going to be making more money once the new Gateway station opens and running times increased.
“For the past three years staff have been promised time and time again that the roster will get better and the working life balance will get better with more weekends off,” he said.
“We have now been advised that this current roster will be in place for a year minimum. Staff have had enough and time for action is needed.
“The staff are fed up with the company agreeing to extended running times – for Hogmanay, the Fringe and rugby events – without discussing it with staff.
“We always find out about it in the news first and the company just alters shifts to suit themselves without regard to staff’s personal life.”
It is understood about 80 per cent of tram workers are in the union. The employee claimed most staff would back strike action if required.
A trams spokesman said: “The proposed changes, which we’re still consulting on, are about fixing a historical anomaly in shift patterns that affects some of our drivers, as well as helping the service to grow.
“An expanded tram operation is good news for all of our staff and for the people of Edinburgh.”