Four hundred workers from The Pension Regulator will take part in a new 12-day strike starting later this month.
Public and Commercial Services (PCS) union members will stage a strike which will begin on 28 February.
Staff will walk out on: 28 and 28 February and 1, 4, 5, 6, 13, 14, 15, 18, 19 and 20 of March.
Members of the union have already taken over 10 weeks of action over pay, causing backlogs at the Brighton-based body.
Workers began their 37th day of strike action last month.
According to the union, employees are angry about being told the body will not give them a large enough pay rise this year, while continuing to spend elsewhere.
The union said PCS members were being offered a 3% pay rise while other civil service employees have been awarded a 4.5% pay rise.
Fran Heathcote, general secretary at the PCS union, said TPR needed to prioritise its staff if it wants to end the action.
She said: “Our hard-working members are angry at being told TPR can’t afford to give them a pay rise to help them though the cost-of-living crisis but they can afford to pay £6m to consultants, splash out almost £200,000 on fees and expenses for its chair and part-time board members and spend more than £1m on other expenses, including accommodation.
“It’s time for TPR to invest in its staff, not on jollies and outsourcing.”
The union claims that its membership at the TPR has risen by 163% since the dispute started in September and it says its strike action is creating a backlog of work as well as disruption to the TPR’s “ability to deliver on their statutory duties.”
According to the PCS, staff at the TPR to strike include lawyers, project managers, actuaries, enforcement officers, some senior managers, admin staff, facilities and tech support.
