Clinton and Johnson attended services at the Northminster Presbyterian Church Sunday (Photo Credit: AP)

(CNN) - BET founder and prominent Hillary Clinton supporter Bob Johnson said Sunday he is 'insulted' with the Obama campaign's latest criticisms of Clinton, and appeared to take aim at the Illinois senator for his admitted drug use as a young man.

"As an African American, I'm frankly insulted that the Obama campaign would imply that we are so stupid that we would think Bill and Hillary Clinton, who have been deeply and emotionally involved in black issues when Barack Obama was doing something in the neighborhood that I won't say what he was doing but he said it in his book," Johnson said while campaigning with Clinton in Columbia South Carolina.

In a statement released by Obama's campaign Sunday afternoon, former South Carolina State Rep. "I.S." Leevy Johnson, an Obama supporter, said he was offended Clinton did not condemn Johnson's comments.

“It’s offensive that Senator Clinton literally stood by and said nothing as another one of her campaign’s top supporters launched a personal, divisive attack on Barack Obama,” he said. “For someone who decries the politics of personal destruction, she should’ve immediately denounced these attacks on the spot.”

Clinton's campaign says Johnson was not referring to Obama's past drug use, but rather his career as an organizer and state legislator. Meanwhile, Rep. Stephanie Tubbs Jones, another African-American supporter of Clinton, said of the comments, "Sometimes people say things that aren't sanctioned ... I can't speak for Bob."

Later Sunday, Johnson maintained the comments were not in reference to Obama's drug use: "My comments today were referring to Barack Obama's time spent as a community organizer, and nothing else," he said in an issued statement. "Any other suggestion is simply irresponsible and incorrect."

In Obama's 1995 book Dreams of My Father — a book that was little read at the time, but recently reprinted — the future presidential candidate writes he was once headed in the direction of a "junkie" and a "pothead."

Referring to his emotional struggles as a young man, Obama writes, "Pot had helped, and booze; maybe a little blow when you could afford it. Not smack, though."

Last month, Clinton New Hampshire co-chairman Bill Shaheen resigned his post after suggesting Republicans would likely raise the issue in a general election.

"The Republicans are not going to give up without a fight … and one of the things they're certainly going to jump on is his drug use," Shaheen said then. "It'll be, 'When was the last time? Did you ever give drugs to anyone? Did you sell them to anyone?'"

Both campaigns are locked in a heated back and forth over recent remarks from the New York Democrat and her husband that have touched off concerns among some African-American voters. Clinton has alleged Obama's campaign is distorting the remarks - an accusation Obama has called "ludicrous."

Related video: BET founder on Clinton, Obama

- CNN's Sasha Johnson and Alexander Mooney