|Gerry McCann admits child alert app 'may have found Madeleine'|
Gerry McCann spoke out as he and his wife Kate urged the public to sign up to the Child Rescue Alert system.
He said: "Every parent has lost their child even if it is momentarily - in a playground, in a supermarket - and knows how terrifying it is."
Heart consultant Mr McCann and former GP Mrs McCann were joined by their actor friend Hugh Grant and parents of lost children in support of Children Rescue Alert.
Mr McCann told ITV's Good Morning Britain: "I'm sure it would have increased the chances of finding Madeleine."
His wife commented: "The people are a crucial resource and are very willing as we know from our own experience."
She added: "The Child Rescue Alert is based on the Amber Alert System in America - already 685 children have been reunited with their families so we know it works."
The McCanns were joined by Coral Jones whose five-year-old daughter was snatched by killer Mark Bridger near her home in Powys in October 2012.
Mrs Jones said: "If we had all this before we would have had more of a chance of having April home."
Four Weddings and a Funeral star Grant said: "To let everyone in the country know that this child is missing, with a photograph, could mean the difference between life and death.
"The first hour or two is crucial and it is a good function for a smart phone. It is a brilliant idea."
The dedicated app sends out alerts as soon as a child disappears. So far 58,000 people across the country have signed up to the scheme.
National Crime Agency figures reveal a child is reported missing in the UK every five minutes. During 2012 -2013 there were 306,000 reports of missing people.
|Madeleine in Pumpkin Outfit|
"The Child Rescue Alert enables members of the public to receive the alerts for vulnerable and high risk missing people straight to their phone and they can help get that child back very quickly.
"You can register at www.childrescuealert.org.uk"
Three year old Madeleine disappeared in Portugal's Praia da Luz in May 2007 while her parents were dining nearby with friends.
The couple, both 46, from Rothley, Leicestershire, believe their daughter, who would now be 11, could still be alive.
Mrs McCann has previously said: "As a parent of an abducted child, it is the most painful and agonising experience you could ever imagine."
Of course this is a brilliant idea. The fly in the ointment is that many people are not going to want their cell phone ringing, or buzzing, every five minutes. Hopefully there is a way to regionalize the alerts.