Kris just called in to "TMZ Live" from Australia (where Kendall is alive and doing a photo shoot) ... and told us she's on a mission to hunt down and punish the person who LIED about her family to the L.A. County Dept. of Children and Family Services.
As we previously reported, officials visited Kris' Calabasas home last month after receiving multiple "tips" from an anonymous caller that the kids were in danger.
Kris says ... besides the LIE about Kendall, the caller had also told officials Kris had beaten Kylie with a belt on a specific date.
But investigators quickly realized it was all bogus ... because when they arrived to the home, Kendall was hangin' out at the house. Kris says Kylie wasn't even in the country on the day of the supposed belt attack.
Now, Kris says ... she's hired people to unmask the bogus tipster ... who she believes is a tabloid reporter.
"We are investigating and have a pretty good idea who it might be."