According to latest government data, the number of children with education, health and care (EHC) plans or statements of SEN attending private, voluntary and independent (PVI) nurseries has risen 54 per cent since April 2014 when the SEND reforms were introduced.
Between 2014 and 2018, the overall number of children aged under five with an EHC plan of SEN statement has grown by 11.25 per cent, from 11,250 to 12,516.
But over the same period, there has been a 54 per cent increase in children in this group attending PVI nurseries - from 956 to 1,476 - according to the National Day Nurseries Association (NDNA), which undertook the analysis.
NDNA said the reforms and expansion of funded childcare to 30 hours a week have stretched local authority budgets, resulting in insufficient funding being given to nurseries to meet the additional support needs of SEND children.
NDNA trustee Helen Gration, who is managing director of Yorkshire Montessori Nurseries, claimed that the company does not receive enough money to fully support children with SEND for all their hours in nursery, even when these have been set out in an EHC plan.
Gration said: "With the government's expansion to 30 hours [funded childcare], we have more children with additional needs and they are attending for more hours per week than previously.
"Each local authority we come across is working differently on this issue, creating a postcode lottery for children.
"Many councils are not offering the full support a child needs for all the hours they are at nursery. This approach is causing significant problems for providers and letting down our children."
NDNA members have also reported that the delay between identifying a child with SEND and receiving a statement or EHC plan, is often longer than the government target of 20 weeks, which it says it achieves for 65 per cent of all cases.
Year-on-year increases in numbers of children in this category have been charted since 2010 - with an 11.3 per cent rise in 2018.
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Purnima Tanuku, NDNA chief executive, said: "These latest figures show that more children with SEND are being identified and supported in PVI nurseries. This backs up the experience of our members as families access funded hours.
"Identifying issues with development at the earliest opportunity can make a massive difference to a child with additional needs. Ensuring that the appropriate support is in place can help with their education as well as social and physical development.
"While it is good news that more children are being identified, the challenge then lies in securing the resources to ensure their needs are fully met.
"We know that local authorities are struggling to pay these costs for all those who need it. The government's own evaluation of the 30 hours childcare policy reported that early years teams were not able to achieve this for children receiving 15 hours of childcare, let alone 30.
"This lack of adequate resources means that nurseries are being left in a vulnerable position when they have identified children in their care needing support, but are not receiving the funding needed to fully cater for a child's needs.
"This must be urgently addressed to make sure funded places can be offered to the children and families who need them the most. This could create a situation where children with SEN cannot be offered places because either the support is not available or the additional cost is too high for families to afford."
The Department for Education has been contacted for comment.