A shortage of graduate teachers working in the early years sector means many young children are at risk of falling behind before they start school, a charity warns.
Save the Children says there are nearly 11,000 too few early years teachers working in nurseries across England.
It says all children should be in childcare led by graduate early years professionals for the best start.
The government says the charity's claims are misleading.
Save the Children's warning comes a week after Education Secretary Damian Hinds said it was a "persistent scandal" that youngsters were starting school unable to communicate in full sentences or read simple words.
What did Save the Children find?
The charity analysed data obtained through Freedom of Information requests to the Department for Education.
It concludes that 10,731 nurseries, playgroups and children's centres - out of a total of 21,041 - do not have staff with qualified teacher status (QTS), early years teacher status (EYTS) or early years professional status (EYPS).
QTS is typically held by school teachers, while EYTS and EYPS are broadly equivalent and focus specifically on early years education.
The charity estimates that this means that some 325,000 children are at early years facilities where there is not a staff member with one of these accreditations.
'Early years are not getting the support'
Leonora qualified as an early years teacher two years ago, but she found the pay and general conditions poor.
So she has decided to move to Poland to work in an international school there.
"The early years are so important, but they're not getting the support," says Leonora.
She was surprised to find that the qualification she had completed left her not much better off financially and felt that it was not highly regarded.
"My salary would only have gone up slightly. The final blow was that during my placement I spoke to the head of the school and she questioned why I'd done the qualification.
"The perception was that it wasn't very good.
"It felt demeaning. No-one does the job for the money, but it needs to be more attractive when you consider the amount of work you go through to get it.
"I was trying to gauge what this qualification job had got me. What is it worth?"
Even so, Leonora does not regret taking the early years qualification, saying she has learnt a lot from it.
"The qualification is really important. You get so much extra knowledge and it teaches you so much in terms of supporting children, especially their personal, social and emotional skills.
"It's been really beneficial. The depth of the theory, I understand so much more. The way you think about coaching children when they are emotional is so different."
But she feels the early years career path needs to be more widely respected to make it attractive to new recruits.
Why is Save the Children concerned?
The charity fears a shortage of qualified teachers in early years settings will have a negative impact on children, particularly the more vulnerable.
"Children who start behind, stay behind," says Steven McIntosh, Save the Children's director of UK poverty.
"But high-quality childcare, led by graduate early years teachers, can ensure children are ready for school. So instead of lowering ambitions for childcare quality, the government should keep its promise to address the crisis in training, recruiting and retaining these underpaid and undervalued teachers.
"All of our little ones should have access to nursery care led by an early years teacher. Without action, we'll be letting down our next generation."
Mr McIntosh says addressing "this chronic shortage" of early years teachers should be at the forefront of Mr Hinds's ambition to improve social mobility.
"But many early years teachers are leaving the profession or are close to retirement and the numbers starting training are plummeting.
"This is hardly surprising when official figures show that investment in promoting early years teacher training is less than 1% of what is spent on school teachers."
What did Mr Hinds say last week?
In a speech on social mobility last week, Mr Hinds said: "It is a persistent scandal that we have children starting school not able to communicate in full sentences, not able to read simple words.
"This matters, because when you're behind from the start you rarely catch up. Your peers don't wait, the gap just widens.
"This has a huge impact on social mobility."
He pledged to halve the numbers of youngsters beginning their schooling without the early speaking and reading skills they need at that age.
How has the government responded to the figures?
Children and Families Minister Nadhim Zahawi claimed the quality of early years childcare had risen since 2010, with 94% of providers rated good or outstanding.
"This government wants every child to have the best start in life, which is why we are investing more than any other [government] in supporting early years education and childcare - around £6bn a year by 2020.
"Most recently the secretary of state announced a £20m fund to provide training and professional development for early years staff in disadvantaged areas to increase their ability to support children's early speech and language development.
"Save the Children's claim is misleading, university study is just one route into the early years workforce. There are over 250,000 dedicated professionals in the private or voluntary early years workforce, with many coming from apprenticeship or on the job training routes."