5:25 PM PT -- Lisa Barlow tells TMZ ... "Bart Carlson was once a business partner in a restaurant in Park City and, I thought, a friend. I am deeply saddened that he has decided nine years after our restaurant business ceased to claim that I owe him money. To be very clear, the claim that I owe Bart or his company money is untrue. I pay my bills and obligations and I always have. In addition, Bart has no interest in Luxe Marketing or Vida Tequila and did not invest in either business. I look forward to the truth coming out and I intend to hold Bart fully accountable for any damage this personal attack may cause me or my businesses."
Lisa Barlow and 2 companies she's associated with -- including her tequila brand -- are facing a lawsuit that alleges more than $400k was loaned out ... but never paid back.
The 'Real Housewives of Salt Lake City' star, Vida Tequila and Luxe Marketing are all named defendants in a lawsuit brought by a guy named Bart Carlson -- who claims he's a longtime personal friend of Lisa -- over loans he says he made to her starting over a decade ago.
The way Carlson tells it ... Lisa came to him in 2010 and told him she and her businesses were experiencing financial hardship, and she needed lotsa cash to cover expenses.