The force said the staff cuts, which would result in a loss of 72 posts, were a result of financial pressures.
"We have to react to financial pressures so that we can continue to serve the public in the most effective way," Chief Supt Mark Holland said.
A Unison spokesman said the cuts would have "a devastating effect" on community policing.
Nottinghamshire's police and crime commissioner Paddy Tipping, who promised to increase the number of PCSOs when he was elected in 2012, said: "We have to make significant savings to balance the budget.
"We are doing everything we can to cut back on non-staff costs.
"However, there comes a point when you have no other option but to cut back on staff numbers. It's regrettable but unavoidable."
Unison representative Dave Ratchford said "Unison will be campaigning vigorously against these cuts."
But he added: "We sympathise with the force as these cuts have been imposed by a government driven by a fanatical opposition to public services," he said.
Mr Ratchford said PCC consultations showed that 67% of residents said they would be willing to pay more for policing.
The force announced earlier that it is shutting four police stations and five front counters in Nottinghamshire to help save Â£2.4m from its budget.
Ch Supt Holland said: "Every community will still have a Neighbourhood Team but under our proposals it will have a different mix - including officers, PCSOs, specials, and our partners.
"By changing our model we can also make sure that our PCSOs are in the places where they are needed most."
He said combining financial and HR functions with Northamptonshire and Cheshire Police Forces had helped reduce the force's budget.
A quarter of Nottinghamshire's 319 police community support officers could be cut under new budget proposals.