Trade union Amicus has branded proposed changes to redundancy, holidays and sick leave as a "massive attack" on its members.
It says more than 85 per cent of members voted to reject the new terms and conditions, which are being introduced for new employees and recommended for existing staff, in a recent advisory ballot.
But the charity's management says 209 out of 370 members of staff have already voluntarily signed up to the new terms and conditions. The new contract will also be accompanied by a "substantial pay increase" for around half of all employees.
This is the second time in three years that Citizens Advice has been hit by an industrial relations dispute. In 2001, strike action was threatened over a performance-related pay system, which the union claimed discriminated against ethnic minority staff.
Amicus staff at Citizens Advice are currently being balloted on potential industrial action. The result is expected in three weeks.
Amicus regional officer Carolyn Simpson said: "A 'yes' vote will send a message to management that its staff want to defend their terms and conditions for current and future employees. I hope we can resolve this matter but I will back whatever action my members choose to take."
But Citizens Advice director of communications Simon Bottery, slammed the ballot as misguided. "We have a good and honest position, and we are disappointed. This has the potential to do harm to both bureaux and clients," he said.
Citizens Advice say that new contracts have been "benchmarked" against deals offered by 30 organisations in the public and voluntary sectors.
Staff accepting the new deal will receive "goodwill payments" of between £750 and £2,000. "Other voluntary organisations will be gob-smacked that we are facing a strike when we have an offer of a salary increase," said Bottery.
The Citizens Advice ballot is another sign that the sector's reputation for good staff/management relations is slipping. But Chris Ball, national voluntary sector secretary at Amicus, denied the sector was facing a new mood of militancy. But he added that people were "tired of being pushed around".