Nearly 100 workers employed by Valley Vets in South Wales will strike again next week following an initial walkout in July.
Workers employed by the private veterinary practice, such as nurses, support staff and vets, will strike between 23 August to 31 August.
Workers have already taken industrial action, which began with an initial walkout from 16 July to 30 July, followed by further ongoing strike action from 6 August to 23 August.
The workers will therefore be on strike for 26 days this month.
Unite the union said staff had been "suffering from low pay that has left 80% regularly borrowing money to meet their basic living costs".
"The company is attempting to heap more misery on its workers by in some cases only offering a pay increase of between one and 1.5%," the union said.
"This is a substantial real terms pay cut as the RPI rate of inflation at the time the pay rise was due stood at 3.3%."
Valley Vets is owned by VetPartners, which recorded gross profits of £553m in 2023 – an increase of nearly £120m from the year before.
The firm has branches across South Wales including Caerphilly and Ystrad Mynach.
Unite regional officer Paul Seppman said the disruption caused by the further strike action was "entirely the fault of Valley Vets and VetPartners".
"Despite the severe disruption industrial action has already caused the company has not been prepared to enter into proper negotiations," Mr Seppman said.
“Our members are chronically underpaid. A company with this kind of wealth should be paying decent wages and providing decent conditions which its hardworking staff fully deserve."
