It was ‘whore’-ible lie.

A Co-op City woman claims her ex got revenge on her for breaking up with him — by claiming she was running a whorehouse.

Things took a nasty turn for Vivienne Fullerton when she ended her “social” relationship with Junior Simpson, who then allegedly sent a letter to the complex’s management claiming Fullerton “ran a house of prostitution from her Bronx premises,” she charges in a lawsuit.

The letter prompted Co-op City security to investigate and speak to Fullerton’s neighbors about the claim, which Fullerton said is “defamatory” and “wholly false.”

Fullerton is seeking $1 million in damages from Simpson, along with $12,000 in monthly parking costs she shelled out for him while they were together.

Simpson could not be reached for comment.