Staff at Bucks County Council will be handed £750 if they agree to change their terms and conditions.
There are currently 13 standard pay grades at the authority, with another six for senior managers.
Each pay range has three or five steps and staff currently move up one step each year, providing their line manager is happy with their work.
Under the plans staff will not automatically move up until they have reached their set targets.
The authority says the changes will bring the council into line with most of the private sector.
The system is based on a new performance management system (called DSP or Delivery Services Performances) which has been trialled by the council during the past 12 months.
Documents seen by the Bucks Herald show that 84% of the 888 staff who responded to a survey about the new system voiced concerns about it.
Unions have reacted with horror to the proposals, calling it ‘a bribe’. They claim it will fuel ‘division’ in the workplace and cause a rise in industrial tribunals through complaints about favourtism.
In an open letter to staff unions say: “In these times of recession, where the council needs to make savings of millions of pounds, do you think that the council will be making a proposal that puts more money into the pockets of employees?
“Or do you think they are anticipating a reduced (controlled) pay bill as a result?
“If the scheme is truly beneficial to employees, as implied by the council, who on earth would all unions be totally opposed to it.”
Penny Gray, secretary of the Bucks branch of Unison, said: “We feel it (the new performance management system) can’t be applied consistently and fairly because there are so many varied roles within the council. The majority of staff themselves do not like it.
“This offer is a bribe which was never discussed with us.
“It’s £750 to be paid at Christmas, it’s a bribe plain and simple and can only be interpreted that way.
“We are wondering how suddenly this money can be found when we have had a number of redundancies, when our day care centres are closed and after unsuccessful outsourcing.
“We are also concerned that those staff who do not sign up for it, how they are going to be treated in the future?
“We will have a two-tier workforce and none of this has been equality impact assessed.”
The new payment scheme would not apply to staff based in Buckinghamshire’s schools.
A council spokesman also confirmed that ‘no-one will have their current basic salary reduced as a result of the changes’.
Peter Cartwright, cabinet member for finance and resources at the council, said: “This change is fundamentally about a culture change.
“We want to allow everyone to see that their pay rises will be linked to their achievement against objectives rather than time served.
“It is many years since we reviewed the way staff are paid and this is the right scheme for the world as it is today.
“High performance and rewarding high performance is integral to how we work, and should be reflected in everything we do.
“Despite the financial pressures we are under, this change is not about cost cutting.
“We have very many excellent staff and this scheme is designed to further incentivise them to provide really good services for residents and businesses in Buckinghamshire.
“Not only will it help us to recruit and reward confident, ambitious officers in future – it also strengthens our ability to hold on to the talented people in our current workforce by recognising and rewarding hard work.”
In the future staff members who join the scheme will be automatically signed up to the new pay arrangements.
The £750 is a taxable one-off payment and the council stresses that staff will be able to voluntarily choose whether or not to take part in it.