A task force set up to examine how local authorities can protect frontline services said councils needed to make a radical shift.
The report said local authorities needed to make a move to protect frontline services by sharing staff, reducing the number of council buildings and sharing professional expertise to find savings.
The idea is that services to residents will not be hit. But GreenSpace business development manager Dave Tibbatts said: "The idea that in the next couple of years we are not going to see changes in service delivery is a fantasy. It's pre-election posturing.Generally speaking, it doesn't ring true.
"Notwithstanding anything that the Government says about high-level savings, we know that parks budgets are being cut and that will inevitably impact on services."
The task force report includes practical advice for councils and examples of savings that can be achieved by making changes.
Regional efficiency experts will provide advice for councils, according to the Department of Communities and Local Government. Parks consultant Sid Sullivan said: "There are natural limits to economies of scale and a limit to how much that can be done with less."
In Oldham, talks are already underway about the possibility of sharing a chief executive with neighbouring Rochdale Metropolitan Borough Council. Parks manager Steve Smith said: "There is some merit to squeezing a bit more out of the back office."