Democratic presidential contender Joe Biden said Thursday he believed that new tax policies were needed to "right the market" during a historic period of economic inequality.

"There are certain things that you have to right the market a little bit. And the market is that if you have all of the tax breaks, essentially all the tax breaks, all of the benefits flowing to the top one tenth of one percent, there's never been as great a concentration of wealth, including going back to the Great Depression, ever," Biden said.

The comments came during an interview with CNBC's John Harwood in Iowa, where the former vice president has embarked on an eight-day bus tour.

He also appeared to support a new financial transactions tax, which has been embraced by rival candidates Sens. Elizabeth Warren, D-Mass. and Bernie Sanders, I-Vt., but which Biden did not include in his economic plan released this week.

Asked why he had rejected the plan, which aides were reportedly considering, Biden suggested it would not raise much revenue, but embraced it otherwise.

"No, I still think we should do that. That doesn't raise the kind of money — I think we should have a financial transactions tax," Biden said.

Biden said that he focused on what he thought he could accomplish.

"I focused on what I think I could get done, get done quickly and pay for everything I'm talking about," he said.

Biden has managed to hold onto his strong polling lead in the Democratic presidential primary, though he has recently fallen to fourth in polling averages in Iowa, which hosts the party's first nominating contest.

On Wednesday, Biden released the details of a new economic plan that his campaign says will raise $3.2 trillion over the next 10 years.

The plan calls for an increase of the corporate tax rate to 28% from 21% and a minimum tax of 15% on the nation's most profitable companies, directed at corporate giants like Amazon that have reaped vast sums while paying little or nothing to the government.

Biden has said that the funds will go to paying for his policy proposals related to education, climate and health care.

The interview came shortly after Biden engaged in a testy exchange at a campaign event with a voter who accused Biden, without evidence, of securing his son a job on the board of a Ukrainian energy company while Biden was vice president.

Biden called the man a "damn liar" and "fat," though a spokesperson later said in a post on Twitter that Biden was not referring to the man's appearance.