More than a quarter of a million young children are at risk of falling behind by the age of five because of a severe shortage of qualified nursery teachers, a charity has warned.
Youngsters who do not have access to highly qualified staff are almost 10% less likely than their classmates to be reaching a good level of development - such as being able to speak in full sentences and follow basic instructions - when they start school, according to a report by Save the Children.
The numbers of applicants for early years teaching roles has plummeted, leaving nurseries, which are also coping with funding pressures, struggling to plug the gap.
The charity is calling on the Government to invest in a qualified early years teacher for every nursery across England, starting with the poorest areas, including Blackpool, Oldham, Birmingham and Barking and Dagenham in east London.
The report, based on new analysis of official figures, concludes that in 2015/16, half of all three and four year-olds - more than 280,000 children - attended a private, voluntary or independent setting without a teacher who held a degree-level early years qualification (equivalent to qualified teacher status) working directly with them.
A child's chances of accessing a nursery with a highly qualified member of staff depended heavily on where they lived.
Children in the West Midlands were least likely to have access to an early years teacher (58% in nurseries without a qualified staff member), while youngsters in the North East were most likely to be taught by a qualified teacher.
The report estimates that a three-year-old who attends a nursery without a highly qualified member of staff is 9% less likely to reach a good level of development at five than a youngster who does have an early years teacher.
Three-year-olds who do not attend childcare are 55% less likely to reach a good level of development than a pre-schooler who goes to a nursery with a qualified member of staff.
Figures show that last year, 860 people applied for nursery teaching roles, down from 2,300 the year before, the charity said.
Gareth Jenkins, director of UK poverty at Save the Children, said: "As a country, we need to start recognising that if we want to give every child the best chance in life - no matter what their background - they must have the support they need to learn, grow and develop in the early years of their lives.
"Nurseries do an incredible job nurturing our children, but many are struggling to afford and recruit the qualified teachers they need to give children this support and support their workforce with more training and development.
"If the Government is serious about creating a country that works for everyone, it's crucial we urgently invest in a qualified teacher for every nursery across the county - giving children the support they need to reach their full potential."
Official figures show that this year, 69.3% of children achieved a good level of development nationally, up three percentage points on 2015.
Sue Learner, editor of daynurseries.co.uk, said: "We are extremely worried by this report. The first five years of a child's life are crucial and help shape the adult they become, with qualified nursery teachers playing an important role in this.
"However it is not surprising there is a shortage of early years teachers with the Government failing to give them the same status and pay as teachers in primary schools."
A Department for Education spokesman said: "To date, we have trained over 16,000 specialist early years graduates and a record number of providers are now rated good or outstanding.
"But we want to get the best staff working in our nurseries and pre-schools so that every child has learnt the basics before they start school and can go on to reach their full potential.
"We are developing a workforce strategy that aims to remove the barriers to attracting, retaining and developing great people and we will be investing a record £6 billion in childcare by the end of this Parliament. This is backed up the fairer funding system we are introducing for early years providers, so that money goes to the areas that need it most."