Roger Stone, a long-time friend and adviser to Donald Trump, has used the racial slur “negro” in a live interview with a black radio host who grilled him on why he thought the US president spared him from jail.

Stone was supposed to serve three years and four months in prison after a federal judge convicted him of lying to Congress and obstructing an investigation into Russian interference in the 2016 election.

He was due to enter prison on July 14 – until Mr Trump intervened and commuted his sentence on July 10.

In a question about why Stone believes he was pardoned by Mr Trump, radio host Morris O’Kelly suggested it was due to his friendship with the president.

“I do believe that certain people are treated differently in the federal justice system. I do absolutely believe that,” Mr O’Kelly said during a 30-minute interview with Stone.

“But I also believe that your friendship and relationship and history with Donald Trump weighed more heavily than him just wanting to make sure that justice was done by a person in the justice system, that you were treated so unfairly.”

“There are thousands of people treated unfairly daily. Hell, your number just happened to come up in the lottery. I’m guessing it was more than just luck, Roger, right?”

After a brief pause, Stone then muttered to someone on the other end “I don’t really feel like arguing with this negro”.

Tweet from @axwise1

Mr O’Kelly then asked Stone to repeat the comment but he became momentarily silent.

“I’m sorry you’re arguing with whom? I thought we were just having a spirited conversation. What happened?”Mr  O’Kelly said. “You said something about ‘negro.'” 

Stone said he had not. “You’re out of your mind,” he said. The interview then continued.

Mr O’Kelly later characterised “negro” as the “low-calorie version of the n-word”, saying on Twitter “I am nobody’s NEGRO”.

Tweet from @MrMokelly

In a statement, Stone defended himself by saying that anyone familiar with him “knows I despise racism!”.

“Mr O’Kelly needs a good peroxide cleaning of the wax in his ears because at no time did I call him a negro,” Stone said.

“That said, Mr O’Kelly needs to spend a little more time studying black history and institutions. The word negro is far from a slur.”

He cited the United Negro College Fund and the historical use of the word.

At one time, “negro” was common in US vernacular to describe African Americans but by the late 1960s, the word was scorned by activists in favour of such descriptors as “black” and some view the antiquated word as derogatory in most uses.

In his statement, Stone noted that some of the program’s audio was garbled and alleged that there was cross-talk from another radio show and that his sound was cut off.

-with AAP