“American Idol” judge Simon Cowell pelted his co-star Paula Abdul with withering put-downs all last season — and this year the acid-tongued Brit has turned up the heat!

Insiders on the FOX talent show — whose January 21 second-season debut was the highest-rated entertainment program in the network’s history — say Simon’s backbiting has left Paula a red-eyed wreck who bursts into tears from his relentless gibes.

“It’s worse off than it is on camera — 100 percent,” Simon admitted in a recent interview, referring to his put-downs of Paula.

“The difference is on our show, we can show how much we dislike each other, whereas on certain shows you have to pretend to like each other.”

Simon isn’t joking about his seething dislike of Paula, said an insider.

“Last season, there was a lot of friction between Paula and Simon. Some people even teased them that it was sexual tension.

“But this time around, it’s just unbridled hostility coming from Simon — and Paula doesn’t know how to defend herself. At this point, it’s a very one-sided war!”

Simon is an expert at finding people’s weaknesses and he knows how to zero in on Paula’s insecurities — her two failed marriages and her hopes of jump-starting her music and choreography career, the insider disclosed.

“Simon’s poison put-downs have left Paula a mess on a regular basis.

“He’s always hated Paula’s den-mother persona. He believes she’s given contestants on the show way too much false hope and encouragement. Paula really roots for the underdogs on the show.

“On the other hand, Simon has become rich and famous for being brutal and he believes his callousness is part of his charm.”

Simon has now gone into full attack mode. Just the day before the debut of the second season, he appeared on “Live with Regis & Kelly.” And when he was asked if he and Paula were dating, he sneered: “If (Paula) was the last person left on earth, I’d eat her. She would be chopped up, smoked, O.K., that’s it.”

Paula is fighting back. In one exchange in the season premiere, Simon accused Paula of being a bore. He sniffed, “I wouldn’t be excited even if you stood naked in front of me.”

Paula snapped back, “Well that’s a given,” implying that Simon isn’t interested in women at all.

Another time she told a reporter that Simon had “been fighting over my lace dress” with her.

“Paula is an ambitious woman who has had her share of hard times in show business, but she’s never had someone so in-her-face and unrelenting as Simon,” said another source.

“He regularly calls her a ‘cheerleader,’ referring to her days as an L.A. Lakers girl — even though she was also a highly respected choreographer for the team.

“On one show Paula made a positive comment to a contestant and Simon arched his eyebrows at her and said, ‘Spoken like a true belly dancer.’ “

He also accused Paula of being on the show in a lame attempt to land a new husband after two divorces, according to the source.

“His remarks about her not being attractive to him are one thing. But when he mocks her career or her failed marriages, it hits her where she’s most sensitive and her eyes well up in tears.

“The stress is really taking its toll on her emotions and on her face. On several occasions, makeup artists have had to scramble to make her teary eyes look less puffy.

“Simon sees Paula’s pain and that eggs him on. Co-judge Randy Jackson often takes her aside and urges her to ignore him, but she can’t.”

Paula doesn’t even refer to Simon by name — she calls him “the rat” or “Simple Simon” or “the cold-hearted snake,” the source added.

“Producers love the sparks between them and it’s great for ratings. But Paula is telling friends that if Simon doesn’t settle down, the show won’t be big enough for the both of them.”