Mauricio Umansky says Lala Kent is a "f***ing liar" for the way she brought up his DM on her podcast.

ICYMI ... the "Vanderpump Rules" alum spilled some tea on her "Untraditionally Lala" podcast last week, saying Kyle Richards' ex slid into her DMs while they were navigating their split.

She said Mauricio asked her to grab a coffee because she talks about him on her podcast ... but Lala said she never opened or responded.

She said she wasn't sure whether he was trying to do damage control or had other intentions. But either way, the podcaster swore there was "not a chance" she would agree to that.

But as Mauricio was leaving Craig's in L.A. Tuesday night, he told the photog he did DM Lala ... but not in the way she implied.

The real estate agent said he hit Lala up because she was "talking s***" ... and he'd prefer if she said her piece to his face.

And as far as not opening his message ... Mauricio's calling BS. He said he sent her a long message, and the coffee invite was at the very bottom.

He claims that in order to know he had asked her to coffee at all ... she would've had to open the message. Mauricio tells us he's toying with posting the receipt to set the record straight.

Stay tuned!