While rumors first surfaced Shelton filed for divorce two weeks ago after hearing Lambert had cheated on him with two men, now sources from Lambert's camp are coming forward and insisting Shelton was the one who was unfaithful, TMZ reported.
In addition to one unnamed man, Shelton, a 39-year-old The Voice coach, reportedly called it quits on his four-year marriage when he learned Lambert, a former Nashville Star finalist, had hooked up with country singer Chris Young.
However, Young has denied such speculation and doesn't want his name to be dragged through the mud.
"I don't normally address gossip but in this case I will," Young, a former Nashville Star winner, tweeted Tuesday.
"My name has been mentioned as a contributing factor in Blake and Miranda's divorce. That is totally FALSE. They are both my friends and I would not betray that friendship. Just wanted to clear that up. Love you guys - CY."
While TMZ is claiming Shelton is "very upset" in the wake of the separation and had no choice but to file divorce paperwork, sources close to Lambert say Shelton cheated on his now ex-wife with a famous country artist.
The sources said Shelton utilized a powerful PR firm to attack Lambert, 31, before she could defend herself or tell her side of the story.
As a result, the couple's divorce is "so bitter," according to the website, that Shelton forced Lambert to get all of her exotic animals off his Oklahoma ranch on the very day their divorce was finalized.
Shelton and Lambert announced their split on Monday "with heavy hearts" by releasing a joint media statement that read "this is not the future we envisioned."
The pair met in 2005 at a CMT event while Shelton was still married to his first wife, Kaynette Gern. Shelton divorced Gern in 2006, and he and Lambert reportedly began dating shortly thereafter. Shelton and Lambert tied the knot in May 2011 after six years of dating.