All six workers at a hostel run by the homelessness charity St Mungo’s will go on strike for a week over a dispute about pay and conditions.
Unite said the dispute was caused by the charity’s refusal to align the pay and conditions of the workers with the rest of the charity’s workforce.
The charity said it was disappointed to hear of the action but would make arrangements to keep the hostel open.
Members of staff at the Sanctuary used to work for a different charity, called North Herts Sanctuary, before St Mungo’s took over managing the hostel in 2011.
Unite said St Mungo’s had agreed to employ the staff on its terms and conditions, which would be better than those that the employees had and would cost the charity £5,000 a year, but had recently reneged on that agreement.
Adam Lambert, Unite’s convener at St Mungo’s, said the charity had ignored the union’s requests for meetings about the strike after talks broke down in September.
He said the majority of the charity’s 800 employees were members of Unite.
A spokeswoman for St Mungo’s said it had had ongoing discussions with Unite for about 10 months. She said the charity believed the six staff had been offered a "good deal".
Nicky Marcus, Unite’s regional officer, said: "The staff members have been forced to take this action as the management has acted in bad faith. It promised to align the staff’s terms and conditions to that of the rest of the workforce – but then reneged at the last minute.
"The six members are St Mungo’s employees. They adhere to St Mungo’s shifts and duties, and are subject to St Mungo’s policies and procedures.
"However, they work more hours for less pay than other St Mungo’s workers. They have less holiday entitlement and an outdated 'discretionary' sickness policy that St Mungo’s management has used, outrageously, over the last year to refuse any sick pay, whatsoever, to workers undergoing cancer investigations and surgery."
Elizabeth Harper, St Mungo’s regional director, said in a statement: "This is an issue relating to a 17-bed local service for homeless people that we have been working to modernise from an overnight-only service to a 24-hour service.
"We are disappointed to hear of the industrial action because we believe we have offered the six staff concerned a good deal. The service will remain open, however, and we will seek to minimise any impact on residents."