Christie Brinkley's hubby promised his 19-year-old secret lover that he would dump his supermodel wife for her, sources told The Post.

Architect Peter Cook, 47, plied Diana Bianchi with a car, promises to boost her singing career and bundles of cash so she could move out of her parents' home in Long Island, N.Y., and further "into his web," the woman's lawyer said Sunday.

Cook would bizarrely leave wads of cash stashed in random spots around Southampton, Long Island, — sometimes hidden under rocks — for Bianchi to find after he told her where they were via e-mail, sources said.

"She was a victim of this guy who preyed on her naivete, her immaturity, the fact that she's 19," said Bianchi's lawyer, Joseph Tacopina.

"There's just so many things wrong with what this guy did."

The lawyer said Cook openly talked to Bianchi "about wanting to leave" Brinkley.

Now, Cook will likely get his wish — but as the result of an expected divorce battle.

The Post has learned stunning new details of what led Brinkley last week to reveal that she was pulling the plug on her decade-old marriage.

Sources said Brinkley got wise to Cook's relationship with the much-younger woman after she was told about it by Bianchi's stepfather, Brian Platt.

Platt approached her at Southampton High School's graduation, where she was speaking, to drop the bombshell.

Soon afterward, the disbelieving Brinkley had a second meeting with Platt, a Southampton Village police officer, about his allegations. She also met with village police officials at the police station, although it was not immediately clear exactly what they discussed, sources said.

The "Uptown Girl" then confirmed the allegations by having a computer expert check Cook's computer, where salacious e-mails between him and Bianchi were found, sources said.

An aspiring singer and Southampton HS graduate, Bianchi first caught Cook's eye last summer while she was working in a toy store on tony Jobs Lane, where he was shopping for his and Brinkley's two young kids, a source said.

He continued dropping by the shop over the summer, and then, when she was expected to be laid off because the store was to close for the season, he offered the petite, shapely woman a job at his architectural firm.

She accepted, becoming his assistant, and a romantic relationship blossomed, sources said. While he wooed her with gifts, Cook whimpered to Bianchi that he wished they were the same age, sources said.

Another man whom Bianchi had been dating at the time grew suspicious about their relationship. And Bianchi's stepfather, Platt, also found out about their affair, and confronted Cook, telling him it was inappropriate and should end, sources said.

Cook agreed, and Bianchi left his firm. Bianchi then moved to Brooklyn, N.Y., to live with her sister Danielle.

But Cook couldn't stay away.

The architect continued to contact Bianchi, at least once going to Bensonhurst to leave a note on her car — a Nissan Maxima that he helped her buy, sources said.

The duo then rekindled their romance, according to sources.

Bianchi's sister told their stepdad what was going on, and Platt then again confronted Cook, sources said.

Tacopina said Bianchi's family retained him partly because she could be a witness in Brinkley's and Cook's expected "bitter" divorce over $60 million-plus in property — and also because of potential legal action that they may take against Cook for his conduct toward Bianchi.

"The issue here is what this guy has done to her. I think the harm will be irreparable," Tacopina said.