This is not true. For example, a good rule of thumb is to increase the IAS by 2% for every 1000ft of altitude. If a certain airplane stalls @35 kts @ sea level, 2% of 35=0.7. so at 10,000 ft, this airplane will stall at an IAS of 42 kts
TallPaul is right. I got screwed up here[&o] This is an example of how to get severely confused with all these speeds.