Skylar Grey has launched her legal team on an ex-boyfriend who allegedly threatened to release sexually explicit photographs and videos of the singer unless she pays up.

Grey -- who recently performed with Eminem on SNL and is featured on his new album, "Revival" -- had her legal team send a cease and desist letter to Michael Hays, who they claim has "taken illegal efforts to extort and harass" the singer.

According to the letter sent on December 13, and obtained by The Blast, Grey's legal firepower claims Hays' actions constitute "criminal extortion," and threaten to report him to the police, U.S. Attorney, FBI and local prosecutors if he continues to "blackmail" the singer.

They claim Hays has threatened to not only release sexually explicit photos and videos of Grey, but that he has also been posting videos on YouTube claiming she actually stole the lyrics she has famously written for Eminem over the years. The reps say those claims are absolutely false.

Grey's team claims they have already investigated Hays for themselves and discovered he is a "felon with a history of serious convictions." They promise Hays, "If your repugnant conduct continues, your criminal history guarantees you will face significant jail time." They also threaten financial ruin by telling Hays "You will be subject to millions of dollars in liability for compensatory, punitive and consequential damages that will require you to declare bankruptcy."

The letter spells it out in black and white -- "Ms. Grey will not give in to your blatant attempt to extort money from her."

The lawyers also claim they have already contacted the Indianapolis Metropolitan Police Department and other law enforcement agencies and "advised them of the situation." They claim Hays can be arrested whenever the cops are given the "green light."

They want Hays to immediately destroy all the material he has on Grey, remove any postings, and basically never speak her name again.

The Blast spoke with Michael Hays, who is adamant "I have never mentioned money or sex tape or pics to Skylar Grey or ANYBODY for that matter." He also has strong words for Grey's attorney, who sent the letter, claiming "The way in which you threatened me is highly unethical for a lawyer per the state of California and I am filing a formal complaint to have you disbarred." He also has a message for his ex-GF, "as for Skylar, bye Felicia!"