New claims: Spencer Pratt claims to have a sex tape featuring his soon to be ex wife Heidi Montag and Karissa Shannon, pictured
Just when it seem things couldn't get any worse for Heidi Montag, Spencer Pratt is threatening to release another sex tape of his soon-to-be ex-wife, but this one doesn't involve him.
Instead, he claims, it features her with Playboy Playmate Karissa Shannon. Pratt was seen this weekend entering the Malibu home the couple shared to remove some of his belongings and apparently stumbled across an X-rated video of Montag and Shannon, reports TMZ.
Shannon and her twin sister Kristina, moved into the Playboy mansion with Hugh Heffner in 2008, but left at the beginning of this year, although they continue to appear in the E! reality TV series The Girls Next Door about life at the mansion.
Shannon told TMZ that the tape does in fact exist but is not convinced that Pratt actually has a copy of it. She added that if the tape does make it into the public eye, she plans to sue Spencer.
Shannon,20, took to her Twitter page earlier today and sent Pratt a very clear message: '@spencerpratt: F*** YOU!!!!'
Montag had a similar message on her Twitter page: '@spencerpratt: F U!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!'
Pratt responded by tweeting: 'Seriously? You're going to start s*** on twitter?'
He also posted another tweet about the alleged sex tapes claiming: 'The sex tape will not feature any bisexuality. It will however feature trisexuality. Also - a triceratops.'
This is now the third tape that has allegedly surfaced, with the first two involving Pratt, with one showing Montag before her extensive plastic surgery and another after.
Montag, 23, underwent 10 procedures in just one day in her quest for 'perfection' last November.
She had already had a nose job, collagen lip injections, and implants that turned her A-cups into 32-Cs.
Heidi has sent emotional messages to her Twitter followers just hours after news broke that her estranged husband was shopping around a sex tape.
The former Hills star told her fans she was 'crying' after adult entertainment company Vivid confirmed that Spencer Pratt had approached them about the video.
Before... and after: He also says he has X rated video footage of Montag pre and post surgery, seen in 2007, left, and earlier this year
'Please send me your prayers and love I need it!' the seemingly distressed reality TV star wrote.
Yesterday news broke that Spencer was trying to negotiate a deal for the supposed tape he made with Heidi.
Vivid Entertainment boss Steve Hirsch said he had not yet seen the footage but had been speaking to Spencer about a possible deal.
'I just got off the phone with Spencer Pratt about a sex tape with Heidi Montag,' he said.
'We are in early negotiations to possibly come to terms for a deal.'
Spencer and Heidi in happier times
Spencer, 27, added: 'I've been making films since I was in the seventh grade. I'm looking forward to people seeing my directorial debut.'
News of the sex tape came just days after Spencer revealed he is writing a tell-all book about his relationship with Heidi.
Heidi has threatened to sue over the book and it seems she is not happy to hear about the sex tape either.
'Heidi's really p***ed off,' the couple's friend Cougar Zank told a celebrity news blog.
'She denies there is a sex tape. She's furious that Spencer would try and embarrass her like this.'
Heidi's pal Jennifer Bunney added: 'She would never put out a sex tape of herself. She's extremely religious and concentrated on getting her life to where she wants it to be.'
Montag filed for legal separation from Spencer in June this year, citing 'irreconcilable differences' as the reason for their split.
This week it emerged that she has served him with divorce papers. The publicity hungry couple, who were married for 15 months, are expected to finalise their divorce on Valentine's Day next year.
Back in 2007, Pratt was accused of spreading rumours that his former Hill's co-star Lauren Conrad had filmed a sex tape with another member of the reality show, Jason Wahler, who denied one existed.
Earlier this week, Heidi told TMZ in relation to the tell-all book: 'This is exactly why I left him, right now I'm looking into my legal options.'
Spencer earlier revealed he will open up about his failed marriage with the reality star and her relationship with her mother, Darlene Egelhoff, in the book.
He told Us Magazine: 'My last book, How to be Famous, didn't make the New York Times best-seller list because it was in the self-help section.
Here's the gruesome twosome from The Hills doing what they do best (pretty much all they do, really) at club AREA in West Hollywood, California: During this grand event, Spencer Pratt hosted the party while the great Ya Boy himself performed his hit single, "We Run LA." 
