Friends, Family Call Spencer and Heidi Liars

Spencer Pratt and Heidi Montag's split is all a big lie, according to some friends (yes, they have some) and family member close to the plastic pairing.

So who's telling the truth?

According to sources cited by Us, Heidi and Spencer fabricated their split in a desperate attempt to stay famous as The Hills wraps up its final season.

Adds an insider, "Heidi and Spencer are laughing over it and having a blast." Even Heidi's sister, Holly Montag, Twittered that the couple are "liars."

That wouldn't surprise THG one bit if it were a complete sham, but TMZ broke the story, "blindsiding" Heidi, whose rep confirmed the separation.

What gives?

HOAX PERPETRATORS? Speidi checks THG to see if we're buying it.

Heidi's new/old BFF Jen Bunney says she and Heidi are doing a single-girls reality show and Heidi only waited to leave Spencer because of The Hills.

"She waited for The Hills to be over to split. Now she doesn't have to pretend," Bunney says, adding that Speidi rejected a fake divorce Hills plot.

But others say the two are simply in publicity-seeking panic mode. Speidi's breakup "is the latest part of Spencer's master plan," an insider says.

Even Bunney says there are no divorce papers filed, and hints at a reunion on their show: "That will be a big aspect ... how Spencer handles it."

This whole Speidi split is ...