Barbara Walters -- Lindsay Lohan's Jay Leno Interview Is a Slap in the Face

Barbara Walters is straight-up insulted that Lindsay Lohan canceled an interview with her to chat with Jay Leno instead -- claiming Lindsay's people didn't even have the courtesy to explain why she pulled out.

Barbara spoke out on "The View" this morning, saying, "If they'd said to me 'You know, Barbara, she isn't up to the kinds of questions that you might ask' ... If they had told me that, I wouldn't feel quite as disappointed as I do today."

Next thing Barbara knew, Lindsay's people had booked her on Leno instead -- and she's insinuating ... it's because Leno won't ask the hard-hitting questions Barbara wanted to.

Lindsay's Leno interview is supposed to air next week.

She refused to talk to Barbara -- but you'll recall, Lindsay opened up about her family problems on TMZ Live just last month. The interview was explosive.