"They've changed working conditions for staff employed by the royal family, including bringing in shift work," Carlos Zarco of the union CSIF told The Local.
Explaining why palace staff were going on strike, the union representative said: "In the past, staff attached to the Royal Palace worked eight hours a day, but from now on people could be working from six in the morning to six in the evening."
"Also, employees will only get half an hour for lunch, and the room they have to eat in doesn't even have air conditioning."
The changes in work conditions were introduced in early January and include unpaid overtime and salary cuts of 15 percent, Zarco said.
The strike by royal staff is planned for March 28th and 29th with 500 employees contracted to the Presidential Ministry taking part.
Staff walking out include gardeners, drivers, waiters, doormen, gatekeepers and museum guides, among others.
Zarco said that the strike was being held in Easter week because that was one of the busiest times of year at museums including the Royal Palace in Madrid and El Escorial.
With entry prices at these museums ranging from €10 to €17, and with 100,000 visitors expected on those days, El Pais reported that the strike could have a big economic impact.