The Democratic vice president drew fire when he contended Republican policy proposals would put Americans "back in chains," Politico reported.
"Look at what they value, and look at their budget. And look what they're proposing," Biden said of the federal budget proposed by Paul Ryan, the Wisconsin congressman Romney has selected to join him on the GOP presidential ticket.
Romney "said in the first hundred days, he's going to let the big banks write their own rules -- unchain Wall Street. They're going to put y'all back in chains," Biden said.
Romney campaign spokeswoman Andrea Saul said the Obama campaign "has reached a new low."
"The comments made by the vice president of the United States are not acceptable in our political discourse and demonstrate yet again that the Obama campaign will say and do anything to win this election," she said. "President Obama should tell the American people whether he agrees with Joe Biden's comments."
The Wall Street Journal reported the crowd in Danville, Va., which included many African-Americans, cheered and booed following Biden's remarks.
Obama deputy campaign manager Stephanie Cutter told MSNBC Biden's comments were not out of bounds because they were a metaphor for the consequences of rolling back Wall Street reform.
"The bottom line is that we have no problem with those comments," Cutter said.
Later, Biden made another campaign stop at the Coffee Break Cafe in Stewart, Va., where he warned patrons Republicans want to "voucherize" Medicare and said if Obama is re-elected "there will be no changes in Social Security -- I flat guarantee you."