Kate - whose daughter Madeleine disappeared on holiday in Portugal in 2007 - attended the launch of the 116000 missing children hotline, and the re-launch of the official missing children website, Missingkids.co.uk, ahead of International Missing Children's Day tomorrow (25th May).
Speaking at the launch, Kate said the new Europe-wide phone hotline was 'really positive'.
"In the last few years there's been greater awareness and certainly there's been a greater political will," said Kate. "We just need to keep spreading the message. It is a big problem, and we do need the Government's backing."
The new hotline is free, confidential and available 24 hours a day. It is operated by specialist support groups in 16 European countries, including France, Spain, Germany, Italy, Portugal, Greece, Holland and Poland.
The charity Missing People will operate the 116000 phone line in Britain, with specialist UK police agency the Child Exploitation and Online Protection centre (Ceop) in charge of the website.
In addition to the hotline and website re-launch, 300 black cabs carrying appeals for missing children inside will operate in and around London.
It was revealed that more then 140,000 children go missing in the UK every year. That is one every three minutes.
Martin Houghton-Brown, chief executive of Missing People, said: "Disappearances such as Madeleine McCann's tragically demonstrated the need for co-ordination across the world when a child goes missing.
"116000 is introduced so that people can call when someone disappears, regardless of which EU country they are in."
Equalities Minister Lynne Featherstone added: "The Government has set a clear direction for this with our missing children and adults strategy, calling on local and national organisations to prevent, protect and provide support for missing children and their families. "
For more information on International Missing Children day visit Missingkids.co.uk.