The statement comes as the government confirmed a £700m cash boost for SEND on Friday (30 August), as part of a £14bn schools funding package.
The move was hinted at last week in leaked documents, though is £100m short of plugging the claimed £800m funding gap.
Some 80 per cent of parents of SEND children are critical of the system - with the majority saying it is impacting on their child's mental health, education and family's finances, according to the joint statement from the Royal College of Speech and Language Therapists (RCSLT) and the children's charity I CAN.
Their verdict on the SEND reform that came into force in the Children and Families Act (2014) is that a central purpose of the reforms - to make the system less adversarial - has not been fulfilled.
The statement adds that there are ongoing "serious concerns" that support for children and young people with speech, language and communications needs (SLCN) has not improved, and that "in many areas it has worsened".
A survey of 241 parents and carers of children with SLCN found that nine out of 10 say they have to fight to get support for their child.
It was also intended to ensure families and children are more involved in decisions around their support.
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They point to figures that show that the number of SEND tribunal appeals, relating to decisions around EHC plans, totalled 6,023 in 2018, an increase of 47 per cent on 2014's figure.
I CAN and the RCSLT want Prime Minister Boris Johnson to develop a cross-government strategy for children and young people and improve the training of newly qualified teachers so that they better understand children's speech and communication needs.
The government should also fund a national programme of training for education staff working with children with SCLN.
Better training is also needed in other sectors where there is a high prevalence of children with SCLN, says the statement.
This includes the care and justice systems, mental health specialist support and alternative education provision for those excluded from school.
"We strongly support the intentions of the reforms: to enable the participation of children and their parents in decision making, to improve early identification and intervention, and to increase collaboration between education, health and social care services," says the statement.
"However, good intentions are not enough. More than 1,800 days since the reforms came into effect, many children and young people with SLCN are not getting the support they need."
Last year the RCSLT and I CAN said they also had "grave concerns" over government action related to SLCN policy and in response to issues raised in 2008 through the landmark Bercow report.
This found that parents were struggling to access information and faced long waiting times for support for their child.