The report highlighted a significant amount of concern among parents about the state of services.
It commissioned a recent YouGov poll which suggested less than a third (27%) of respondents felt the Welsh government was doing enough to support child health.
It found 18% of respondents believed the Welsh government’s NHS spending on child health was “about right”.
About two-thirds (68%) of respondents believed the cost-of-living crisis is having a negative impact on child health.
The college has called on the Plaid Cymru government to honour its manifesto commitment to develop a Children’s Health Plan.
It argued the plan should focus on three key priorities – revolving around data, targets and investment.
RCPCH co-officer for Wales Dr Lizzy Nickerson said: “Wales urgently needs a clear and ambitious Children’s Health Plan that puts prevention, early intervention and reducing inequalities at its heart.
“This must be evidence-based, data-driven and shaped by the expertise of clinicians alongside the voices and experiences of children and young people themselves.
“We need stronger, more transparent child health data, meaningful targets that allow progress to be measured, and a clear focus on closing the gap between children living in the most and least advantaged communities.
“Children’s health cannot be an afterthought – it must be a long-term priority for the Welsh government.
Wales’ children’s commissioner, Rocio Cifuentes, said: “Children have the right to the highest attainable standard of health, yet this report shows that too many children in Wales are being let down by widening inequalities and inconsistent access to support.
“The findings echo what children and young people have consistently told me – that support often comes too late, that access to services such as mental health and dental care can be difficult, and that healthy choices are not always the easiest choices.”
A Welsh government spokesperson said it had a “comprehensive range of policies and programmes” which played a “crucial role” in improving health outcomes for children in Wales, with early years development, vaccination, and mental health support “central to our approach”.
“We know the early years of a child’s life are crucial, not only for their development but also for shaping their future health, wellbeing and life chances,” they said.
“We are considering options to provide a stronger and more sustained national focus on babies, children and young people’s health, ensuring prevention, early intervention and integrated service delivery remain at the forefront of policy and service development in Wales.”