The RSPCA is planning to dismiss staff who do not agree to a performance-related pay scheme that the charity’s recognised union warned could exacerbate a staffing crisis at the charity.
The move, which would affect more than 1,700 staff members in roles ranging from fundraising to animal care, has been branded "a backwards step" by the union Unite.
Unite also expressed concerns about a culture of bullying at the charity.
The RSPCA said in a statement that only annual increases would be related to performance and that staff had been reassured their basic salaries would remain the same.
Third Sector understands that staff members who have not agreed to sign a new contract, which Unite said would also include a two-year pay freeze and overtime reductions, by 31 March will be dismissed from the charity.
The charity had an income of £142m in the year to 31 December 2018, up from £140.9m the year before, but spent £159.8m, the first time expenditure has outstripped income in at least the past six years.
In a statement, Unite said the new contracts represented "an attempt to provide animal welfare on the cheap" and would introduce unnecessary bureaucracy.
Siobhan Endean, national officer at Unite, said: "What we have here is a management that wants to take a sledgehammer to a carefully crafted incremental pay scheme and introduce a performance-related pay scheme, but how you evaluate ‘performance’ when it comes to rescuing abused animals remains to be seen.
"The RSPCA already faces a recruitment and retention crisis, and morale is low. This will get worse if pay and terms and conditions are eroded."
In a statement, the union said a recent RSPCA staff engagement survey had revealed that 31 per cent of the charity’s workforce had either been bullied directly or witnessed bullying.
It said the survey of Unite members at the charity had found that 76 per cent did not feel performance-related pay was suitable for their role and 80 per cent thought it was inappropriate overall given the "negative workplace culture".
But Endean said: "There is still an opportunity for the management to have a reboot in the way it treats its workforce and we urge them to take this course before we have to consider a ballot for industrial action."
In a statement, the charity said it rejected the idea of a recruitment and retention crisis or low morale.
A spokeswoman told Third Sector: "As a charity funded by public donations it’s crucial that we regularly review our pay and reward framework to ensure it is fair, modern and affordable, and we use money wisely to fulfil our mission to help animals."
"The current framework was due to be reviewed next year, but this has been prioritised because the RSPCA, like many charities and organisations, is facing a challenging financial environment. This review is one part of a broader programme to ensure our costs are better in line with our income so we can do even more for animals that depend on us.
Under the proposals, she said, increases would be based on affordability, linked to appropriate market pay and recognise the contribution of employees.
She said talks with Unite, which began in October, had been "constructive and open" and the charity remained committed to working with the union.
She said there was "no place for bullying" at the RSPCA and policies were in place to help protect staff.
A new people and culture strategy had been developed after the employee survey, she said, which included a wellbeing action group run with Unite.