Strike action is threatened if two social workers are disciplined over the death of a four-year-old boy.
Public service union Unison said it would "defend our colleagues to the hilt".
Brighton and Hove City Council confirmed an investigation into the workers' role in the case had been completed and separate disciplinary hearings would be held.
Social workers last October occupied the offices of social services director Allan Bowman in support of colleagues Dave Pamely and John Barrow who, they said, were being made scapegoats for the boy's death.
Unison branch secretary Alex Knutsen said members would be balloted for strike action if the two were punished.
They were suspended following the death of John Smith on Christmas Eve 1999. He had 54 injuries on his body, including bite marks.
The boy's adoptive parents, Simon and Michelle McWilliam, of Fishersgate, Southwick, were each jailed for eight years for cruelty. They are appealing the sentences.
Injuries on John were seen by the two social workers but there was no attempt to rescue him from the home.
They were hoodwinked by the couple who claimed the boy was self-harming.
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