Kate and Gerry McCann said perseverance and hope will remain during their search for Madeleine, who vanished aged three while the family were on holiday in Portugal.

The message, on the official Find Madeleine Campaign Facebook page, thanked supporters for their persisting solidarity as it "gets harder to know what to say or write" after her disappearance.

More than €13 million has been spent on the police investigation to find the missing girl, who disappeared from the family's holiday apartment in Praia da Luz in May 2007.

The post, written on behalf of Mr and Mrs McCann, reads: "It gets harder to know what to say or write as each anniversary of Madeleine's abduction approaches then passes.

"Life is full and busy which helps but Madeleine is still missing and she is still dearly missed."

"Information continues to come in (incredible as it may seem after so long, although we are grateful for that) and work goes on. Perseverance and hope remain."

Mr and Mrs McCann, from Leicestershire, added: "Thank you to everyone who continues to support us and wish us, especially Madeleine, well.

"After 11 years such warmth and persisting solidarity is truly remarkable, and at the same time a real tonic and boost to our spirit. We couldn't bear for Madeleine to be forgotten or to become just a 'story'.

"She is a real person and still our 'little girl' and as we always have, we will endeavour to do whatever it takes to find her. Thank you so much for staying with us on this mission."