Turning Point has said it is "constantly" reviewing costs and working out how to protect jobs in the face of "significant cuts in funding".
The charity said the proposals put forward to Unite "have not been made lightly" but are "forced out of economic necessity".
In a statement yesterday, Talking Point said that negotiations are continuing to progress. However, Unite, which has 500 members at the charity, claimed that talks had "broken down" and management had "threatened to sack its workforce" and offer re-engagement on "shabby" new contracts.
Unite said that industrial action is one of the options being considered, as some of its members could be out of pocket as much as £10,000 a year.
Unite regional officer Jamie Major said: "This is something Turning Point does not need to do. Its own audited accounts prove beyond any doubt that Turning Point is not an organisation in crisis – it is expanding.
"This is a perverse decision – a charity robbing its staff to prop up profits and boost expansion."
Major added: "Any individual who does not agree to these bully-boy tactics will be out of a job.
"We have offered to agree to major concessions to cuts in overtime, 'sleep ins', 'on call', pay rises and the Agenda for Change pay increments, but this was not enough. It seems corporate greed is not exclusive to the bankers.
"We now have our own corporate renegade right here in the charity sector and we will treat Turning Point accordingly by standing shoulder-to-shoulder with staff and fighting this with every tool at our disposal – nothing is ruled out."
In its statement, Turning Point said: "This will affect a lot of people in different ways. However, we need to move towards a market rate for employees, one that protects their base pay.
"Indeed, we are proposing to increase base pay for those who are the lowest paid. The proposals are looking at various enhancements, including those paid for unsociable hours, many of which are no longer paid in the sectors within which we operate.
"We have not gone down this route until it has become an economic necessity."
