Madonna posted the racy snap to her Instagram
She added: "I can't believe you can't recognise your own mother's anus from under the bed."
The picture showed Madonna half under a bed whilst her derriere is on show, as well as her red bottom stilettos.
Lily was clearly in shock as she misspelled her next reply, showing some relief that the photo wasn't actually her mum.
She wrote back: "Ma that was a ducking rollercoaztwr."
Kate's daughter wasn't able to log into her Instagram page at the time so she couldn't even check if her mum posted the pic.
Lily confessed how relieved she was, adding: "I legit sat down to deal w that. My coworker came up and asked if I was on break."
Kate text her daughter the photo
Kate responded: "Lol i'm crying" as Lily joked back: "Me too tears of happiness. I wouldn't even be embarrassed like for me if u posted that I would be concerned."
Kate insisted that she wouldn't even think of posting something like that, calling her daughter a "maniac", to which Lily agreed and explained that is why she was so confused.
The model and actress tried to work out how it'd even be possible for her to take the photo.
She asked her daughter: "Also what am I doing under the bed and when did I get that rug."
Kate's followers seemed to find the prank extremely funny as they took to the comments of the post.
Kate shares daughter Lily with Michael Sheen
One wrote: "'But it's also very arty' oh bless her she was trying so hard to be nice."
A second person said: "Haha but now…does the world deserve a Kate version of this 'art piece'," as another added: "Nothing like mom and daughter laughing and joking."
A fourth commented: "When did I get that rug!?!?!? Amazing conversation!!!"
Madonna posted a series of snaps from the same bedroom photoshoot last Wednesday which featured her posing around the room in revealing lingerie and full glam makeup.