Pressure is being ramped up on Cornwall Council to kill off plans to join forces with a private company and set up a venture to run many of its core services.
The trade union Unison has sent a letter to all 123 councillors accusing the authority's bosses of rushing into hugely importantly decisions with undue haste.
Meanwhile a cross-party coalition of councillors have banded together to have the plans thrown out.
The joint venture company would see Cornwall Council sign an agreement with a private firm to set up an independent enterprise.
The new company would run a myriad of services for Cornwall Council and in theory be able to bid for work from other organisations.
Nick Olgard, chairman of Cornwall's Unison local government branch, said staff were worried and felt they were being told only one side of the story.
"They feel a bit like rabbits caught in the headlights.
"They're being given pretty hefty briefings from their managers but people feel they have not been told an alternative and the message they have is that this is only one game in town."
The joint venture company would involve Cornwall Council linking up with a private sector organisation which would run services including libraries, benefit payments, IT and payroll.
A tender for the long-term project – estimated to be worth between £210 million and £800 million – is being drawn up, with BT and Computer Sciences Corporation in the running to be the private partner.
Unison's letter, which was sent to councillors on Friday and has been seen by the Western Morning News, expresses deep concerns at the "scale and pace" of the proposals.
It says fundamental changes are "being rushed through with undue haste.
"There has not been full and proper consideration of the potential risks; the majority of councillors have been unaware of these proposals and even some Cabinet members have been excluded from important."
Unison is not alone in urging caution and a motion to scrap the plans will go before members from Independent councillor Andrew Wallis, seconded by Mebyon Kernow member Andrew Long and supported by Liberal Democrat and Labour councillors.
Mr Wallis said the proposal was a step too far.
"This would be a real root and branch reform.
"There would be a huge number of services handed over to the private sector, such as council tax and benefits.
"That is the council's core business.
"If this goes ahead, what will Cornwall Council actually do? What is its function? There are also major issues of democracy and governance."