The Childhood Eye Cancer Trust (Chect) said that 72% of children with retinoblastoma (Rb) are not urgently referred on after seeing their GP - contradicting NHS guidelines.
Family doctors initially misdiagnosed the disease as conjunctivitis or a lazy eye, according to a poll of the parents of 39 children with the condition.
The charity warned many children with the disease are forced to have at least one eye removed as the cancer is too far advanced by the time they are diagnosed.
"We have known for years that most families suffer unacceptable delays in getting a diagnosis for childhood eye cancer," said Joy Felgate, chief executive of Chect.
It is crucial that GPs recognise the six main warning signs as a child with Rb may otherwise appear well - which is why our new campaign is so important."
"From the discussions we have conducted with the majority of parents whose children were diagnosed in 2012, it appears the number of delays is worse than we feared.
"This is just the start of our work to gather a firm picture of the problems parents face because some health professionals are not recognising the signs of Rb.
"When a child develops a life-threatening condition we feel the least they should expect is for their frontline health professional to recognise there is a problem and to ensure they receive access to life-saving treatment as soon as possible."
The charity is trying to raise awareness about symptoms of the condition - which affects 50 children in the UK each year.
These are the main symptoms to look out for:
• A white reflex. A white eye, white pupil or white reflection can be seen in a photograph where the flash has been used. This may also be seen when the child is in artificial light or a darkish room.
• A squint
• Red, sore or swollen eye without infection
• A change in colour to the iris
• Deterioration in vision