'Real Housewives of Atlanta' star PHAEDRA PARKS was stunned by a sleazy extor­tion attempt threatening to expose her husband as an adulterer – but she caught the inept blackmailer in an outrageous lie.

The blackmail plot unfolded in early March when the 40-year-old attorney started receiving calls from a stranger claiming she hooked up with Phaedra’s body­builder husband Apollo Nida.

The woman said she had a hotel receipt as proof of the one-night stand in 2012 and allegedly demanded hush money to keep it secret. But furious Phaedra refused to pay up, and in early April the blackmailer posted an account of the supposed night of passion on an Internet blog.

Although the perpe­trator described herself as a 20-year-old college stu­dent, her post was filled with childish mis­spellings and twisted gram­mar. “Apollo told me he was unhappily mar­ried,” she wrote. “I asked him why he didn’t have on his ring but he informed me that him and his wife was sepa­rated.”

The post included a Holiday Inn receipt, but Phaedra immediately knew that the hotel bill, dated Oct. 24, was a fake.

“She and Apollo had spent that day doing radio interviews to­gether to promote their workout video,” said the insider.

The extortion attempt came at an extremely hectic time for Phaedra, who’s about to deliver the couple’s second child. She’s also working full-time at her law firm and taping her own spinoff show for Bravo.

Although attractive women have been known to throw themselves at Phaedra’s handsome husband, the source said: “She trusts Apollo 100 percent.”