Inspectors from Ofsted and the Care Quality Commission visited the town in February and March this year to examine services offered by the council and the Blackpool CCG (clinical commissioning group).
They have highlighted four areas of "significant weakness" including long waiting times for some therapies.
Blackpool must now submit a plan of action, known as a Written Statement of Action, explaining how it will resolve the situation.
The four main areas of concern are - the lack of specificity, ownership and accountability in the area’s improvement strategy for SEND (special educational needs and disabilities); the duties around preparing children and young people for adulthood not being fulfilled; the poor communication with parents and carers across the area; and the long waiting times for some therapies.
In a published letter to the council and CCG, the inspectors say: "The area has not paid sufficient heed to the views of children, young people, parents and carers.
"In some instances, important decisions about key services, such as the short breaks provision, have been taken which have negatively impacted on lived experience of families."
The letter adds long waiting times for services has caused "considerable stress and anxiety".
It adds: "Many parents and carers’ perception is that the area has put barriers in place to make it harder for them to access education, health and care (EHC) plan assessments and specialist short breaks.
"Where there are delays, parents and carers report that these lead to their children and young people’s needs escalating. Families find it hard to cope as a result."
A spokesperson on behalf of the Blackpool SEND Partnership, which includes the council and CCG, said: “We accept the outcome of the inspection and appreciate the valuable feedback the inspectors have given.
“We acknowledge that our progress implementing the 2014 reforms has been too slow but we are now working together on a new SEND strategy to ensure that all children and their families receive the right support in the right way.
“The partnership is aware of delays to accessing some services and the distress this can cause families for which we apologise.
"We are committed to working together to meet the increasing demand across education and health provision. Alongside this immediate actions are being taken to improve communication and support to families while they are waiting.
“Blackpool Council is proud of how co-production a key part of everything that we do in Children’s Services. We now need to make sure that this approach is mirrored across special educational needs and disabilities services.
“Families deserve better and they will get it.”
Martin Thacker, deputy director at the National Deaf Children’s Society, said: “Blackpool Borough Council has a legal duty to support children with SEND, but this inspection shows that its system simply isn’t working.
“It’s clear that major improvements are needed, so it now falls to the council’s leaders to show exactly how they plan to deliver for every child in their care.
"Disabled children can reach their potential and achieve very well at school, but to do so they need the right support. The council must not let them down.”