"This is pure fabrication," he told People Wednesday. "There is no relationship, nor has there ever been one. This is a stupid rumor."
Rumors first surfaced in March, when the tabloids reported that Harris and McGraw had been seen looking cozy at the Chateau Marmont in Los Angeles.
Blakey said the only interactions between Harris and McGraw have been strictly business. "They wrote a song together and that was the extent of their relationship," he says.
The single, "Club Queen," Harris' first, hit iTunes Monday.
So, despite calling off her wedding, things aren't looking too bad for Harris.
"I sing and I write, I've been writing songs and I've just been having so much fun with it all," Harris told Seacrest.
As for that ill-timed Playboy magazine cover?
"It's a beautiful cover and it went to print a while ago, so I hope that people can enjoy it," she said.
For Hefner, however, it's a reminder of what could have been.
"Recent events call for a special sticker on the July cover," he wrote on Twitter, posting a picture of the cover with the sticker "Runaway Bride in this Issue" covering Harris' naked torso.