The BBC's Alison Holt: "The Christmas campaign makes it all too clear what is at stake"

The NSPCC investigation into how people use its own helpline found that one in seven callers kept quiet about their fears for more than a year.

The child protection charity, which works with police and social services, said that many people feared reprisals from violent parents if they reported fears or evidence of abuse.

Others doubted whether their suspicions were strong enough to warrant independent expert investigation.

Hesitation: Helpline staff often receive information too late

The survey of 173 callers was part of the NSPCC's Christmas campaign. Experts say that the risk of child abuse or neglect rises during the Christmas and New Year holiday period because of increased family tensions.

Directors of the charity called on what they believe are the thousands of "silent witnesses" to come forward.

Mike Taylor, director of NSPCC children's services, said: "(During Christmas) some of the seasonal goodwill seems to disappear (in families) and there are greater concerns about the protection of children.

"Perhaps not surprisingly, people do not want to get involved, but linked with that was a fear of reprisals.

Mike Taylor of the NSPCC: "Many people fear reprisals"

"If people are fearful of what an adult might do to them, heaven knows what they are doing to a child in that household."

Mr Taylor said the charity did not expect friends or neighbours to know for sure whether a child was at risk or already being abused.

But he added that they may hold the last crucial piece of evidence to prompt intervention.

If people reported fears to agencies, they would get a "sympathetic hearing", he said.

"If we are going to protect children properly, we need the information so that we can know how best to follow it up.

"If in doubt phone one of the national helplines, such as our own or Childline, and people can get advice.

"If there are any serious matters, tell the police or social services immediately, the child may have injuries that need immediate investigation."

The NSPCC National Helpline number is 0800 800 500.