Donald Trump
U.S. Republican presidential candidate Donald Trump speaks at the Family Leadership Summit in Ames, Iowa, United States, July 18, 2015.REUTERS/Jim Young

Donald Trump's presidential campaign is once again under fire, not for something the Republican candidate said, but for something one of his personal aides said.

Michael Cohen, a special counsel to the real estate mogul turned politician, was forced to apologise after angrily telling a Daily Beast reporter, "You can't rape your spouse." Cohen was responding to allegations that Trump had raped his first wife Ivana during an incident between the two in 1989.

The accusations were made during a deposition given during the couple's divorce. It was later revealed in the 1993 book Lost Tycoon: The Many Lives of Donald J Trump, The Daily Beast reported.

In it, the incident allegedly stems from Trump's anger over a painful scalp reduction surgery. The presidential candidate allegedly held back his wife's arms, pulled fistfuls of hair from her scalp and then violated her.

"Then he jams his penis inside her for the first time in more than sixteen months. Ivana is terrified...It is a violent assault," author Harry Hurt III wrote. "According to versions she repeats to some of her closest confidantes, 'he raped me.'"

The former Mrs Trump later backtracked on her comments and said she had felt "violated" by the experience, but said she did not want her "words to be interpreted in a literal or criminal sense."

According to the New York Times, Cohen works for Trump's company, but does not officially work for the Republican front-runner's campaign.

"You're talking about the front-runner for the GOP, presidential candidate, as well as a private individual who never raped anybody," Cohen told The Daily Beast on 27 July. "And, of course, understand that by the very definition, you can't rape your spouse."

The Daily Beast also claims Cohen threatened to sue the publication if the story was published.

"I will make sure that you and I meet one day while we're in the courthouse. And I will take you for every penny you still don't have. And I will come after your Daily Beast and everybody else that you possibly know," Cohen said. "So I'm warning you, tread very f*****g lightly, because what I'm going to do to you is going to be f*****g disgusting. You understand me?"

"You write a story that has Mr. Trump's name in it, with the word 'rape,' and I'm going to mess your life up... for as long as you're on this frickin' planet... you're going to have judgments against you, so much money, you'll never know how to get out from underneath it," he added.

Cohen apologised for his comments in a statement on 28 July, "Rarely am I surprised by the press, but the gall of this particular reporter to make such a reprehensible and false allegation against Mr Trump truly stunned me." He added, "In my moment of shock and anger, I made an inarticulate comment—which I do not believe—and which I apologise for entirely."

According to the Times, Trump's campaign has opted to distance itself from Cohen's comments, saying, "Mr Trump didn't know of his comments, but disagrees with him." The campaign also provided an endorsement from the candidate's former wife.