Police have unveiled a revamped nationwide alert system aimed at enlisting the public to help rescue abducted children.

The new network, comparable to the amber alert system in the United States, will be compatible with other European countries for the first time. As a result a continent-wide alert could be issued in circumstances where youngsters may be taken across national borders.

Kate and Gerry McCann have campaigned for such a system to be introduced since their daughter Madeleine disappeared in Portugal in May 2007. Mrs McCann will join other relatives of missing children to mark the launch in central London, International Missing Children's Day (IMCD).

Chief Constable Peter Neyroud, head of the National Police Improvement Agency (NPIA), said the actions of police immediately after a disappearance are "vital".

He said: "Through Child Rescue Alert the community is able to form a strong alliance to help in the hunt for child abductors when an alert is activated. It is fitting that the NPIA should relaunch (the) alert on International Missing Children's Day, which forms a poignant reminder of the sense of devastation caused to the parents and families of children who go missing."

Officials have been working behind the scenes for months to iron out bureaucratic hurdles to broadcasting sensitive information. They emphasised how the first hours after an abduction are crucial and that an alert would spread information more quickly.

Although some 100,000 children are reported missing to police each year, senior officers expect the national alert to be used extremely rarely.

The upgraded child rescue alert system will use new computer software to handle a deluge of calls from members of the public. Regional and national television and radio stations will broadcast messages, in some cases interrupting scheduled programmes. Organisers hope to eventually use internet and text messaging as well as motorway information signs.

The system is being co-ordinated by the NPIA and any national abduction alert will be led by Greater Manchester Police. Work on the improved system began after the NPIA won a share of one million euros (£886,000) from the European Commission alongside France, Holland and Belgium. Portugal, Spain and the Czech Republic have already introduced their versions of alerts that link with the European network.

This year, IMCD is highlighting the cases of six missing children: Sigourney Teresa Chisholm, Andrew Thompson, Telvin Timba, Shawn Timba, Sami Odeh and Rami Odeh.