A longtime confidant of rapper Dr. Dre claims the Rev. Al Sharpton threatened to march on the hip-hop icon’s recording studio unless he donated a half-million dollars to charity.

Bruce Williams, Dr. Dre’s former right-hand man, said the alleged extortion attempt involved Sharpton’s displeasure with vulgar lyrics as well as a nasty feud between rappers 50 Cent and The Game.

“He said if we didn’t have [$500,000], we marching. It’s that easy,” Williams said in an interview published on hiphopdx.com.

Sharpton insisted yesterday he never spoke to Dr. Dre and has no recollection of ever meeting Williams.

He called the accusation “absurd.”

Williams maintained that he and Sharpton helped orchestrate the 2005 public reconciliation between the two rappers – who had been battling over The Game’s defection from 50 Cent’s record label.

“When that beef between 50 Cent and The Game went public, Al Sharpton called over and asked for half-a-million dollars,” Williams wrote in his book “Rollin’ With Dre: The Unauthorized Account.”

“Otherwise he was going to bring the heat.

“We gave him $250,000. Then we had The Game and 50 make up in public,” he wrote.

At a press conference, the gangsta-rap stars announced a joint gift of $253,000 to the Boys Choir of Harlem.

Jimmy Rosemond, The Game’s manager, disputed Williams’ account.

“I am 100 percent positive that The Game did not come to the conference in fear of Al Sharpton marching and Rev. Sharpton had nothing to do with that conference or donations affiliated with it,” he said.

Sharpton last April railed against vulgar rap lyrics at his National Action Network’s annual convention.

“I had marched on those companies about the n-word, the h-word, b-word,” he said.

“Why would I do that if I had some deal with them about giving charity?”

chuck.bennett@nypost.com