The NSPCC is calling on the government to offer more help to children giving court evidence against their abusers.
Some children give evidence in court via video links
The charity says there is not enough funding for specialist support services in England and Wales.
It also says many children go into court totally unprepared. About 29,000 give evidence in court annually.
NSPCC chief executive Dame Mary Marsh said abused children have already had "horrific experiences" and that facing court can "reopen old wounds".
The NSPCC and Victim Support conducted a survey of 50 child witnesses to find out how they felt about giving evidence.
They said half did not understand the words being used in court, and almost as many had been accused of lying under cross-examination.
Dame Marsh said: "Without support [children] are left vulnerable and ill-equipped to face interrogation in court and provide robust evidence to convict their abuser and achieve justice."
'Out of touch'
The NSPCC campaign is being led by television presenter Noel Edmonds, who has criticised the judiciary for being "out of touch".
He also said he was shocked by the lack of support available to young people.
"The NSPCC are very keen for me to moderate my language on this but I am very angry that... we still have a situation in a supposed civilised society that children report that appearing in court is worse than the abuse they suffered in the first place," he said.
"That is absolutely appalling."
He said he believed judges were out of touch both with children and public opinion.
"The judge is in total control of his court and he decides if the child should be denied a video link, the right to be screened or that wigs and gowns should remain," Mr Edmonds said.
"They are often gentlemen who have very little experience of young children and the sector of society from which these children are receiving this appalling behaviour."
The NSPCC runs seven young witness support services - in Northern Ireland, Cheshire, Devon and Cornwall, Essex, Hull, Surrey and Swansea.