But he said a slipper's warmth depends on the thickness of the sole, not the lining of the upper.
A slip-on moccasin-style shoe with a sturdy sole was a better option for around home, he said.
Podiatry NZ spokeswoman Caron Orelowitz agreed, saying: "They are not doing your feet any good. They are also hideous and ugly, and apart from the fact they smell because people don't wash them, there is no support in them.
"Wearing them as shoes is not what the product is for. They are expensive slippers but they were not designed as footwear other than slippers."
Baxter said his clients who wore the boots for several hours each night were compromising their rehab from leg injuries because the boot's design often increased the vulnerability of a wearer's feet to stress as they moved around.
Even people who exercised in cutting-edge trainers would sometimes have injuries that lingered because of wearing inappropriate footwear.
Kiwis who had no previous foot problems also risked causing damage from wearing the boots as casualwear.
ACC statistics show there were 11,505 claims in 2014 for injuries relating to footwear, costing $5.9 million.
Figures could not be broken down to those wearing boots.
Ugg Australia, manufacturer of the world-famous Ugg Boot, did not respond to requests for comment.