Negligent misrepresentations are not protected by the First Amendment. They can be a basis for legal liability to someone who is harmed them.
Misrepresentations that are not even negligent can be the basis for liability if they constitute a violation of a warranty, which may be implied in law rather than express.
For example, suppose you sell a piece of art to someone. This is a sale of goods, which comes with an implied in law warranty that the seller has good title to the good sold and is entitled to sell it. By offering it for sale you are making an implied representation that you own it and have a right to sell it. But suppose that the person you bought the art from was actually a thief. Then you would have liability for your implied in law representation that you had good title to the artwork, even if you had a good faith and reasonable belief that this was true.