More than two-thirds of RSPCA employees have so far refused to sign new staff contracts despite being asked to do so by 20 December, according to the trade union Unite.
A Unite document sent to members at the animal welfare charity said only 500 of the charity's 1,700 staff have signed the contracts, which include a controversial new performance-related pay scheme.
The RSPCA had asked staff to sign the new contracts by 20 December and had threatened to dismiss anyone who does not sign by the end of March.
Unite's figures suggest there is little sign of a breakthrough in the long-running dispute between the charity and the union over management's attempts to cut costs.
The union is planning a formal ballot on industrial action after an indicative ballot in December revealed that 88 per cent of RSPCA members supported such a move.
A Unite spokesman said no formal notification for an industrial action ballot had yet been issued.
"Unite is still in negotiations with the RSPCA, and the union believes that this matter can be resolved through a negotiated settlement," the spokesman said.
In a video for Unite members at the RSPCA, Siobhan Endean, a national officer at the union, said Chris Sherwood, chief executive of the RSPCA, was "proposing to rip up your contract of employment, your holiday pay, your sick pay, your pay policy and your maternity rights and put on average around £2,000 cuts on RSPCA staff". The charity disputed these claims.
Asked how many staff had signed new contracts, an RSPCA spokeswoman said: "The society is comfortable with the number of contracts that have been signed to date. They are in line with our expectations and this number is increasing on a daily basis."
She said the charity was "confident the vast majority of staff will sign" but added that the organisation was drawing up contingency plans "in the unlikely event that people do not sign their contracts".
The spokeswoman took issue with many of Unite's claims. "It is simply not the case that all cost savings are falling on employees, and the society is looking at a number of ways to bring its costs under control," she said.
"As repeatedly stated, the society has no plans to change sickness benefit, holiday entitlement or maternity rights as suggested in Unite's video."
"No one’s basic salary is affected by these changes. Any reductions mentioned relate to allowances, which are not a guaranteed part of salary.
"Previously, staff have been earning significant amounts of money on standby, which the charity has identified as an inefficient way of using donations. Money will still be paid for standby and other allowances as well as any work carried out out of hours.
"We are meeting with staff across the country to answer any queries and those who have still not signed their contracts will be invited to individual meetings to have the opportunity to discuss their concerns."
Unite's document urges staff to attend management meetings and "fully voice your concerns".
It says: "The society has stated this is an opportunity to ask questions and no pressure will be placed on employees to sign their contracts at these consultation meetings.
"So, if any member attending feels bullied, intimidated, discriminated against or unfairly responded to in these meetings or at any time, please contact a Unite rep immediately."