A union has accused Watford politicians of making council workers "scapegoats" for the poor performance of the borough’s revenues and benefits department.
In a letter to councillors on Watford Borough Council, UNISON said the department’s problems were due to IT issues and not the efforts of staff.
The union’s comments come after the department found itself centre of a political row between the ruling Liberal Democrat administration and the opposition Labour group.
Last year the Labour challenger in for the May mayoral elections, Jagtar Singh Dhindsa, called for elected mayor Dorothy Thornhill to resign over the amount of benefits being overpaid.
The union sent the letter to borough councillors urging them to oppose proposals to hand control of the department to Three Rivers District Council.
The department has been run jointly by the two councils for the last few years as part of a shared services initiative.
UNISON told councillors the recent reports of failures at Revenue and Benefits "do not tell the whole story".
It said: "Since the outsourcing of ICT to Capita last summer, WBC, TRDC, and shared services have experienced numerous outages and service failures in respect of their ICT services.
"This has especially affected the performance of Revenues and Benefits and the quality of the service it delivers to its service users.
"UNISON Watford speaks for its members when it says that staff and there frontline managers are being made scapegoats for these failures."
Union then attacked the transfer plan as a "retrograde step" saying it would weaken Watford politicians’ power to hold the department to account.
It also argued the transfer would cause further disruption to the department.
Mayor Thornhill said the poor performance of the department had been due to a range of issues not just IT.
However she said recent efforts and a new head of finance were helping turn the situation around.
She added: "There was a range of things, IT included. I am grateful to the staff who have kept bashing on through a very difficult time and it is already turning around."