The NCVO said that Changeup, announced by voluntary and community sector minister Fiona Mactaggart last week, could represent a step-change in government support for the sector.
But its chief executive Stuart Etherington pointed out that funding ends in 2006 and called for the Chancellor to set out a five-year spending plan for Changeup in his July spending review.
He also cautioned that developing the sector's infrastructure should not just be aimed at improving its capacity to deliver public services: "There are many other equally valuable areas of voluntary activity in the community."
Kevin Curley, chief executive of the NACVS, said Changeup was "the most important central government initiative for the local voluntary sector in my lifetime".
But he was concerned that some of the money would be diverted to the nine government regional offices, which would channel funds to local organisations.
"We think the costs of those offices should be met in some other way, so that all the funding is directed to the local sector," said Curley.
Changeup is the Government's strategy for spending more than £80m allocated to infrastructure projects last September. The allocation was prompted by the Cross-Cutting Review of the role of the voluntary sector in service delivery in October 2002.
Some of the money has been used as part of a £6.25m 'early spend' programme announced last December, to set up collaborative arrangements at local level between councils of voluntary service, rural community councils, volunteer bureaux and others.
They will now be able to bid for money from Changeup to start providing infrastructure services, such as financial advice, training or governance, in their areas.
Mactaggart has divided Changeup into three investment programmes - £33m for 'embedding quality and improving reach,' £29m for 'improving infrastructure,' and £5m for 'driving up activity in key service areas'.
The first programme would finance five 'national hubs' that would act as beacons of good practice and direct frontline organisations to support sources.
A Home Office spokesman said that the Government was only able to plan in three-year cycles: "The Home Office is in negotiation with the Treasury for additional funds in this area and we may hear more about that in the spending review next month."
For more information see www.home office.gov.uk/.