The 1% pay rise awarded to over 155,000 NHS Scotland staff has been hit by further delays.
The pay rise was due to be paid in April but health workers will now have to wait until June for the extra money in their pay packets.
Although the pay rise will be backdated to April staff may have to wait even longer for back payments.
Willie Duffy, Head of Health for UNISON Scotland said: "Clearly this is unacceptable. We signed off a circular instructing health boards to implement the pay rise, three weeks ago.
"I was assured the pay rise would be in the May pay packet. Our members will be angry about this given that they have had the pay rise in England, the North of Ireland and Wales and we are still waiting."
"I am going to be writing to the Cabinet Secretary for Health, Alex Neil, to express my anger at the way the whole process has been handled and the fact we were assured it would be paid in May. I will be asking for an explanation from him as to why it has not been."