Probation staff and workers at family courts say they will go on strike if "savage cuts" are made in next week's comprehensive spending review.
The probation union, Napo, said it would co-ordinate the strikes "for maximum impact".
All public services are bracing themselves for cuts on 20 October.
Harry Fletcher, the union's assistant general secretary, said it would be the first probation staff strike for 25 years.
He said: "Kenneth Clarke, the Justice Minister, cannot call for less people to be jailed and instead be supervised in the community and at the same time cut probation."
Mr Clarke has said he wants to see more community sentences instead of short prison terms, but Mr Fletcher said this would be impossible if the probation service was cut back.
At Napo's annual conference in Scarborough Mr Fletcher said: "Ironically, because of his contradictory actions, more people will be jailed as the courts discover that probation is unable to fulfil its statutory obligations."
The Probation Service is expected to cut its 20,000 workforce by 5,000 from March 2012.
It would be the first time in 25 years that Napo members have gone on strike and only the second time in its history.