A majority of family doctors believe financial incentives are encouraging parents to seek ADHD and autism diagnoses for their children.
Research conducted for the think tank by Savanta found that 57 per cent of more than 1,000 GPs surveyed believed monetary benefits were a significant factor behind parental requests for assessments.
The findings come amid growing concern over what the Centre for Social Justice (CSJ) described as a rising "diagnosis industry" linked to sharp increases in child disability benefit claims.
Almost all GPs surveyed, representing 94 per cent, said referrals for suspected autism and ADHD had increased compared with five years ago.
The number of children whose parents receive disability-related benefits has doubled over the past decade to 900,000 and is projected to rise to almost 1.2 million by 2030.
According to the report, the entire increase has been driven by behavioural, learning and ADHD-related conditions.
Annual spending on high-needs SEND provision and child health benefits has also doubled in real terms from £12.4billion to more than £24billion.
The report stated this figure is broadly equivalent to the total annual salary bill for all teachers in England.
Waiting lists for ADHD assessments have increased sharply from around 21,000 in April 2019 to approximately 270,000 by December 2025.
More than 400 private clinics are now operating across Britain, charging an average of £1,361 for each child assessment.
Most GPs believe financial incentives driving ADHD and autism diagnosis requests
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Three quarters of GPs surveyed said they believed diagnostic criteria for autism and ADHD had widened to include behaviours previously regarded as within normal ranges.
Around two thirds of respondents said most children referred for assessments primarily presented with behavioural or environmental difficulties rather than neurodevelopmental conditions.
The same proportion said diagnoses were being issued too readily in cases where behavioural interventions could prove more effective.
The Centre for Social Justice described the polling as the largest survey of GP opinion on children's diagnoses ever conducted.
It identified increased screen time, family breakdown and developmental disruption caused by the Covid pandemic as contributing factors behind the rise in referrals.
Under current benefit rules, a child diagnosed with ADHD whose family receives standard disability benefit support can generate additional annual payments of around £5,500.
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The report said this could rise to approximately £10,000 annually when Universal Credit passported elements are included.
For a single parent receiving Universal Credit with three children diagnosed with ADHD, total child-related benefits could exceed £35,000 per year.
Despite increased spending, the report said educational and employment outcomes for children with additional needs remained poor.
A 50 percentage point attainment gap remains between pupils with and without identified special educational needs.
The report also stated that half of 15-year-olds with both an Education, Health and Care Plan and disability benefits were not in education, employment or training by the age of 22.
That figure was three times higher than the rate recorded among their peers.
The CSJ proposed restricting new benefit claims for children with primarily behavioural or ADHD-related conditions to more severe cases.
It estimated the reforms could generate annual savings of approximately £1billion.
Half of the savings, amounting to £500million, would be invested into Family Hubs to fund parenting programmes focused on emotional and behavioural development.
The think tank also proposed increasing benefits for parents caring for children with the most severe needs by 10 per cent above inflation.
Dr Sanjiv Nichani OBE, consultant paediatrician, said: "Too many children are being medicalised rather than properly supported to thrive and meaningful reform is urgently needed."
Baroness Maclean, the former minister of state, added: "Something has gone badly wrong with how we support children with additional needs in England, but almost no one in public life is willing to say so."