Record numbers of families are using children's centre services but face losing the lifeline unless extra funding is made available, a survey by the 4Children charity found.
According to what the charity said was the only national survey of the services, for the first time more than a million families are now using the centres, almost a third of them disadvantaged.
Almost three quarters (73%) of centres have seen an increase in numbers but 66% are operating on reduced budgets and 31% expect to cut services in the next year as local council funding cuts bite.
Some 2% expect to close altogether, the survey found.
To counter the decline, Pupil Premium funding for deprived school pupils should be extended to early years provision, 4Children joined other campaigners and bodies in recommending.
Much better integration with health agencies and troubled families teams was also required it said - with 62% of Children's Centres not represented on Multi-Agency Risk Assessment Conferences.
Co-ordination with local health agencies was also inconsistent, the survey found - despite the potentially significant savings of joint working for the public purse.
Health visitor clinics are not being run through 19% of centres, ante-natal midwifery clinics not located in 36% and post-natal clinics not based in 57%.
Chief executive Anne Longfield said: "The past 12 months have seen existing pressures on families mounting, with increasing strain on job security, household finances, relationships and widespread anxiety over the potential impact of further austerity cuts to local support services.
"Our census shows that more and more families, particularly those in the greatest need, are turning to children's centres to help pull them through these tough times.
"Local authorities are under extreme financial pressure to make tough decisions, but the long term social and financial rewards will come with filling up, not closing down these crucial centres, which have already provided a cost-effective lifeline for hundreds of thousands of families.
"Rather than contemplating reductions and closures, we should instead seize the opportunity to make the most of Centres' growing potential to help avert family crises.
"This means improving the way in which they pool resources and budgets with local partners; making additional investment; and committing wholeheartedly to keeping their doors open to families of all backgrounds."
The charity also called for universal services from birth to the age of 19 and a statutory requirement for data and information sharing between local authorities, agencies and the centres.
Barriers preventing third-sector organisations from running centres should be broken down, it added.
Shadow minister for children L ucy Powell said: "This report paints a stark picture of the future for children's centres and for the families that rely on them.
"Despite David Cameron's promise to protect Sure Start before the last election there are now 566 fewer children's centres serving our communities.
"David Cameron's cost of living crisis is putting more and more pressure on family life and family budgets. And children's centres are an essential part of the web of support services available to help families.
"Labour's primary childcare guarantee and the extension of free childcare for working parents from 15 to 25 hours will be a real boost for families feeling the pinch and struggling to balance work and family life."
A Department for Education spokeswoman said: "The number of families using children's centres is a real testament to their success.
"Children's centres play a vital role in supporting families with young children - particularly the most disadvantaged - and we have made it clear that all local authorities must provide high-quality services through their centres to improve outcomes for these families.
"There are more than 3,000 Sure Start centres in England and we have increased funding for early intervention services from £2.2 billion to £2.5 billion in 2014-15, ensuring the future of centres even during these difficult times.
"The survey rightly highlights the importance of joint working between education and health professionals, with some children's centres already offering birth registration and incorporating the use of health visitors.
"The introduction of the two-and-a-half-year-old check - combining both health and education - will make sure that centres are able to offer an even more important and valuable service to families in the future."