JUSTIN BIEBER has the hots for VANESSA HUDGENS, and GF SELENA GOMEZ is steaming mad!

“High School Musical” cutie Vanessa, 23, co-stars with Selena, 19, in the upcoming movie “Spring Breakers,” and insiders say “Baby” singer Justin, 18, flipped for Vanessa while visiting Selena during filming.

“Justin spent a lot of time on the set in Florida during the late winter and early spring,” said a source. “He was there to see Selena, but he wound up falling hard for Vanessa. He couldn’t stop raving about how smart, sexy and talented she is. Plus, he loves the fact that Vanessa is like Selena, but minus the goody-two-shoes personality.”

The two struck up a friendship even though Vanessa is dating actor Austin Butler, 20, and they’ve been secretly texting each other since “Spring Breakers” wrapped, said the source.

“Their banter tends to get very suggestive,” the source revealed.

“A mutual friend told Selena about it, and she freaked. Now Selena is threatening to dump Justin unless he cuts ties with Vanessa.”

Meanwhile, Vanessa – who dated her “High School Musical” co-star Zac Efron for over four years before they split in 2010 – is still hot ‘n’ heavy with Austin, who’s starred in the TV series “iCarly,” “Ruby & the Rockits,” “Zoey 101” and “Life Unexpected.”

“Vanessa thinks Justin is adorable and talented, but she’s devoted to Austin and she doesn’t want to betray Selena,” said the source.

“Still, Justin’s crush on Vanessa is creating major tension between him and Selena. Now Justin is trying to get back in Selena’s good graces by vowing she’s the only one for him.”