She said: "Only the abduction theory is possible because we were not involved in Madeleine's disappearance and she did not wander off by herself."
Kate, 41, also slammed ex-Portuguese police chief Goncalo Amaral who she and husband Gerry faced this week in a libel hearing over his banned book accusing them of faking Maddie's kidnap and hiding her body.
She wrote on the Find Maddie website: "His theories damage the search for our little girl. There is no evidence that Madeleine is dead and that we are involved in her disappearance."
Maddie, then three, vanished in Praia da Luz, Portugal, in 2007. The hearing resumes next month.