Many maintained nursery schools are facing closure as local authorities struggle to find a fair way to fund early years education, professional organisations and unions have warned.
A report from the charity Early Education (formerly the British Association for Early Childhood Education) calls for state-funded nurseries to be valued as beacons of excellence rather than face the axe due to a new funding framework.
Megan Pacey, chief executive, said: "There are a number of local authorities struggling to make the single funding formula work and the potential outcome is the closure of maintained nursery schools.
"Whenever there is a problem in another setting, or staff need support or training, it's to maintained nursery schools that the local authority sends them. If they are not there, that brilliant resource will be lost.
"People take them for granted, until they are not there, and then when they are not there people will appreciate how valuable they are."
Government statistics show that there are 439 nursery schools in England, but 83 others have closed in the past 10 years - more than twice the closure rate of primaries. Pupil numbers have fallen by 22 per cent over the same period, compared with 9 per cent in primaries.
Now there are fears that more nurseries will close as the Government asks local authorities to come up with a single formula to fund nurseries, whether maintained, private, voluntary or independent.
Since April, authorities have been expected to move to funding all early- years settings by participation, rather than place, as had been the case in the maintained sector.
The Government has said it recognises that maintained nursery schools are more expensive to run than other state provision and that recent changes are not intended to threaten their viability.
But nursery school advocates say they are now fighting on a number of fronts - a potential drop in funding, the proposal for all children to start reception in the September after they are four, and school reorganisations to shore up falling rolls in primary schools.
Pauline Trudell, vice-president of the National Campaign for Real Nursery Education, said: "It's quite tricky to know at the moment exactly what's going on because local authorities are still working on their formulas. But we are teetering on the brink. We need to act very quickly to prevent closures and amalgamations. There is enormous anxiety among early-years teachers who are working their socks off because they are so passionate about nursery education."