By Mark Smulian
The report for the Improvement & Development Agency found the professional areas hardest hit would be human resources, training, information technology, finance, administration, and facilities and property management.
A 'small but better paid, more strategic, professional elite' will remain within councils in each discipline.
The report also predicts councils will have to share or outsource services where recruitment is already hard, including planning, building control, environmental health and law.
But it found progress on efficiencies from shared services was patchy, despite government encouragement.
Councils had looked for efficiency savings from procurement, but shunned radical change to their workforces. Many had given little thought to the issue.
Joan Munro, IDeA workforce strategies head, said: 'Councils do not seem to have updated their workforce strategies in the light of the [local government] white paper or to have concrete numbers on where jobs will be lost or increase.'
The survey found numerous collaborations among the 10 Greater Manchester councils, but 'many involve few staff. Primarily they are about aggregating demand and procuring services from the private sector', it said.
'Where shared services had significant staffing implications [they] move forward less quickly, or indeed get dropped.'
Alan Warner, director of people and property at Hertfordshire CC, said it was likely the directly employed local government workforce will get smaller.
'But you are not looking at large reductions,' he said.
Steve Holland, procurement programme director for the regional centres of excellence, said: 'Councils have got to look at shared services because it is where they can save money.
'Whether it is front-line services, the services that support them or assets and infrastructure, it is collaboration that will really deliver savings.'
What the report says
* Pressure from the government for efficiency will reduce councils' workforces through shared services and outsourcing
* Councils have sought savings so far from efficient procurement, rather than from staffing
* Counties and districts have looked for savings in unitary bids, but other councils have done relatively little.