As the Republican presidential primary continues its descent into tabloid-level smears, GOP front-runner Donald Trump is laying all the blame at the feet of his chief opponent for the nomination: Texas Sen. Ted Cruz.

"I had nothing to do whatsoever with the National Enquirer, and neither did the campaign," Trump told ABC News in a phone interview Sunday. "And I will tell you -- for him to try and say that I had to do with it try and put the shoe on the other foot is disgraceful."

Trump was referring to a story that ran in the National Enquirer on Friday that claimed to reveal unsavory details about Cruz's personal life. The Texas senator immediately denied the report's allegations and slammed Trump as the "sleazy" originator of the story, along with the campaign's "henchmen."

Get Breaking News Delivered to Your Inbox

But on Sunday, Trump said he "didn't even know about the story" in the Enquirer.

"I have no control over the National Enquirer," he told ABC. "I just got it last night. Somebody sent it to me over to read so I could at least see what it said."

The billionaire businessman then pointed the finger at Cruz, saying his rival was the one who "started" the vicious mudslinging that this week grew to encompass the two candidates' wives.

"By the way, he's the one that started it," Trump said. "And from what I hear, he and his campaign went out and bought the cover shoot. She did -- Melania did a cover shoot for GQ, a very strong modeling picture. No big deal. But it was a cover shoot for GQ, a big magazine. And it was, you know, fine."

The GQ cover image featured Trump's wife, Melania, posing nude on a fur rug and handcuffed to a briefcase. An anti-Trump super PAC unaffiliated with the Cruz campaign used that photo in an ad -- captioned "Meet Melania Trump. Your next first lady," -- that encouraged Utah voters to vote for Cruz over Trump in the state's primary last week. Trump, in retaliation, threatened to "spill the beans" on Heidi Cruz, his rival's wife. Cruz has refuted that he has any connection to the super PAC, called "Make America Awesome," or to its Utah ad campaign.

Despite the denials, Trump insists Cruz was responsible.

"From what I hear somebody bought the rights to it and he was the one or his campaign bought the rights and they gave it to the super PAC," Trump said. "And just so you understand, that super PAC is very friendly to Ted Cruz. He knew all about it 100 percent. So he started it. I didn't start it."

Cruz, on Sunday, again denied the National Enquirer allegations, calling them "complete made up lies."

"They're garbage," Cruz told Fox News. "But, you know, it's indicative of just how low Donald Trump will go."

Responding to Trump's own denial of his involvement in the Enquirer story, Cruz pointed to one source that had once been affiliated with his rival's campaign.

"You know the only person quoted on the record there is Roger Stone, the chief political adviser to Donald Trump," Cruz said. Though Stone departed Trump's last year, when the campaign said they had fired the adviser, Cruz insisted that "Roger Stone remains the henchmen, the hatchet man, the enforcer for Donald Trump. He's pushing these attacks. And, by the way, he's been pushing them for many, many months online."

He also pointed out that David Pecker, the CEO of the tabloid magazine, was a "close" friend of Trump.

"The National Enquirer has endorsed Donald Trump for president," Cruz said. "And this entire campaign they've done two things. One, they've praised Donald Trump at every turn. And two, they spread lies and smears and attacks on every -- every one of his opponents."

Of the ad that featured Trump's wife, Cruz decried it as well.

"As soon as I saw it, I denounced it and said it was wrong," Cruz said. "Melania is a lovely woman."

He added that it was the work of an independent organization.

"It was a group -- I don't know the person who was involved," Cruz said. "As far as i know, I never met them. I've never spoken to them. They're completely disconnected from the campaign."