Just when we thought Miley Cyrus and Liam Hemsworth were on the road to marriage, the 23-year-old pop star is making a mess of things, literally.

Life & Style has exclusively learned that the singer doesn't exactly keep her Hidden Hills, CA mansion clean — and it's driving Liam nuts! "There's dog poop and pee everywhere, old food, pizza boxes, takeout containers, fast-food wrappers and dirty dishes piled up," said the source.

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And that's not even the worst part! The Voice coach is taking her lack of hygiene to another level. "The combination of all that mixed with the constant weed-smoking and the bong-water spills makes the place smell horrible," the source continued.

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It appears Liam is finally fed up with her antics. The 26-year-old Hunger Games actor gave Miley an ultimatum — get your act together, or else!

Her messy abode and bad habits could be the reason the actor confirmed to Australia's TV Week that he is in fact, not engaged.

For more on Miley Cyrus and Liam Hemsworth, pick up the latest issue of Life & Style magazine, on newsstands now!