The Audit Commission, the financial watchdog, and the Office for Standards in Education believe the move would give primary schools a big financial boost.
The report suggests that schools should be funded on the work they actually do, not what they have received in the past.
The "activity-led" reforms would give similar funding for similar work. For example, if it emerged that delivering the national curriculum at 11 required the same amount of work as delivering GCSEs at 16, the two activities would be funded equally. This could allow primary staff as much non-contact time as their secondary counterparts.
"Building equitable levels of preparation and non-contact time into funding for primary school teachers is probably the single most important change that activity-led approaches tend to indicate," says the report.
Their support, in a report prepared for a Government working group on education funding, has given hope to local authorities.
It has also won approval from heads and classroom unions.
But civil servants said that ministers would not endorse the proposals, as they were complex and potentially costly. The Government is proposing a simpler per-pupil entitlement.
The current system of standard spending assessment is based on pupil numbers with weightings for factors such as special needs but is distorted by historical patterns of expenditure