The children’s charity fears plans to devolve commissioning of the services to 42 elected police commissioners will lead to patchy services for children and young people.
It also said the Ministry of Justice consultation paper makes no mention of services for young witnesses of crime. Instead, it said the services should be commissioned nationally but delivered by local teams.
The NSPCC also said children and young people should be consulted about their needs and there should be a separate witness and victim code of practice for them.
Victim Support is campaigning against the reforms because it said the proposals would lead to inconsistent services across the country and would cost £21m to set up.
Victim Support gets 80 per cent of its income from the Ministry of Justice to provide services including a national helpline for crime victims, a community service to support victims of crime and support for them in every criminal court.
The NSPCC is far less reliant on the state for its income: in 2011, £14.8m of its £148.6m income came from government.
Javed Khan, chief executive of Victim Support, said the Magistrates Association, Mencap, Liberty, the Police Federation and more than 100 MPs had also expressed concern about the MoJ’s proposals.
Andrew Flanagan, chief executive of the NSPCC, said: "The NSPCC has helped thousands of children prepare for the daunting experience of giving evidence in court – often helping to convict people who have committed appalling crimes against them.
"If government proposals to locally commission victims and witness services go ahead there is a danger that children in some areas will not be able to get the support they need."
A spokeswoman for the Ministry of Justice said: "We currently spend £66m a year supporting victims and witnesses of crime, and our proposals will raise up to £50m extra. This will increase, not reduce, the support and help on offer.
"Police and crime commissioners will put the needs of victims of crime at the centre of their agenda and will be required by law to consult victims in setting policing priorities in their local areas."