TORI SPELLING fired one of her best nannies just to keep her sex-crazed hubby away from the pretty young blonde!

While sources told The ENQUIRER that her troubled husband Dean McDermott is not involved with the woman, the 40-year-old reality star doesn’t trust Dean around such an attractive female staff member.

Dean, in a shocking admis­sion on the couple’s new Lifetime reality series, “True Tori,” describes himself as “sexually insatiable.”

Sadly, his overheated libido apparently cost the hard-work­ing nanny her job.

“The nanny is single, attractive and twenty-something, and Tori simply didn’t trust Dean around her,” a close source told The ENQUIRER. “Her firing had nothing to do with anything she did. She’s absolutely blameless and was a terrific nanny to Tori’s kids.

“TORI JUST DIDN’T want to put any more temptation in Dean’s way. Their marriage is already hanging by a thread.”

In her 2013 book, “Spelling It Like It Is,” Tori identifies the nanny as “my pretty blonde baby sitter.”

Tori and her 47-year-old husband employ several nannies for their children – Liam, 7, Stella, 5, Hattie, 2, and Finn, 19 months.

But the nanny’s attractiveness began to worry Tori after she was suddenly plunged into a marital nightmare last Christ­mas when Dean’s alleged affair with 28-year-old Canadian beauty Emily Goodhand burst into the headlines.

“Before Tori knew about Dean’s cheating, it didn’t cross her mind that having the nanny around day and night might be a problem,” said the source. “But then she realized it was just tempting fate. It’s sad because the kids ask about her every day – they’re heartbroken.”

Sources say the blonde baby sit­ter first met the McDermott clan in 2011, when the family wandered into a children’s shoe store where she was a sales clerk. At the time, she was pudgy and not too stylish. But after being around her fash­ionista boss, she lost weight and began to blossom.

The devoted nanny spent the entire summer with the family in Ontario, Canada, while they filmed their HGTV show “Tori & Dean: Cabin Fever.”

“She was also a friend to Tori and a shoulder to cry on,” said the source. When Dean had to stay in Toronto to work on his show “Chopped Canada,” she became Tori’s road trip partner, said the source, adding: “Tori and her even joked they were like ‘Thelma & Louise’!”

But eventually Tori became too fearful that the sexy blonde would present an irresistible target for Dean.

As The ENQUIRER revealed last week, the actress is so worried about her husband’s extramarital activities that she is demanding he get tested for HIV and other sexu­ally transmitted diseases.

Recently, sources say the pres­sure of her marriage problems finally got to Tori, as she was hos­pitalized for several days. She was brought home by Dean on April 26.

Now, Tori is busily looking for a Plain Jane replacement nanny.

“Firing the nanny is not what Tori wanted to do, but she felt she had no choice,” said the source. “She’ll never hire an attractive woman to be in her home full time again.”

Tori is busily looking for a Plain Jane replacement to watch their