Sussex Police have launched the second phase of a pioneering scheme to help find abducted children.

It will see text messages sent to registered mobile phones within minutes of a child kidnap.

The first phase, launched in November, saw radio and television stations agree to interrupt broadcasts with information about a child who may have been snatched by a paedophile.

But the police admit the scheme would not have been used the night Sarah Payne was snatched although it is a potential life-saver.

Sussex Police said there was not enough detail about eight-year-old Sarah's abduction to warrant launching its Child Rescue Alert programme until the morning after she vanished.

Questions were raised about the scheme last week when it was not used to help find missing two-year-old Merlin Reid who wondered off into woods near Billingshurst.

Detective Chief Inspector Martin Underhill said the alert would only be issued if four criteria are met.

The child must be under 16, there must be a reasonable belief they had been abducted, a reasonable belief their life was in danger and sufficient information to give the public.

DCI Underhill said: "In the case of Sarah Payne, all we knew on the day she disappeared was that a white van was seen speeding away from where she was last seen.

"There are four-and-a-half million white vans in the UK, so our switchboard would have been jammed with calls if we issued a Child Rescue Alert.

"We could only have launched an alert the next day when we had obtained a description of the van driver, who turned out to be Roy Whiting, from Sarah's brother Lee."

Sarah's grandfather Terry Payne has welcomed the second phase of the project, despite being aware it may not have saved her life.

He said: "We understand why it could not have been used on the night Sarah was taken but we still think it is a fantastic idea.

"Within minutes of a child disappearing, thousands of eyes can be out there looking for them."

So far, 4,000 people have registered their mobile phones but DCI Underhill hopes to sign up at least 400,000.

To register your mobile, visit www.childrescuealert.com or text the word ALERTS, followed by a space, then your postcode to 07786 208080.