WASHINGTON (CNN) -- Ralph Nader lashed out at the Democratic presidential candidates Monday after they said he could hurt their chances of taking back the White House.

The longtime consumer advocate announced Sunday that he will launch his fourth consecutive White House bid -- fifth if his 1992 write-in campaign is included.

In an interview with CNN on Monday, Nader accused Illinois Sen. Barack Obama of name-calling and challenged him to "address the issues."

"Above all, explain why you don't come down hard on the economic crimes against minorities in city ghettos: payday loans, predatory lending, rent-to-own rackets, landlord abuses, lead contamination, asbestos," Nader said.

"There's an unseemly silence by you, Barack -- a community organizer in poor areas in Chicago many years ago -- on this issue," he said.

Nader called Sen. Hillary Clinton the Democrat "most loved by big business," referencing a Fortune magazine article from last year. Watch Nader fire back »

The June article said Clinton had "probably the broadest CEO support among the candidates" at that point.

Many Democrats fear that Nader, who turns 74 this week, could draw votes away from whoever gets the party's nomination, potentially helping presumptive Republican nominee Sen. John McCain win the White House in November. Watch Nader defend his decision to run »

Obama and Clinton were quick to pounce on Nader after he made his announcement.

"He thought that there was no difference between Al Gore and George Bush, and, eight years later, I think people realize that Ralph did not know what he was talking about," Obama said at a town hall meeting Sunday.

Clinton also said Nader "is responsible for George W. Bush" and called his candidacy "regrettable" during a Boston, Massachusetts, fundraiser Sunday night.

"We can't assume that we're going be able to win overwhelmingly," she said. "We're going to have to fight for every state, and Ralph Nader is a problem."

Earlier, Clinton said Nader -- who says environmental policies are central to his platform -- "prevented Al Gore from being the greenest president we could have had."

Nader has long rejected accusations that he served as a spoiler in 2000, effectively helping Bush beat Gore. See how many votes Nader got in 2000 »

Nader stood by his contention that Gore won the 2000 race because he took the popular vote, saying Florida's electoral vote "was stolen from him." Watch former Gore adviser discuss Nader's effect »

Nader said Democrats should "concentrate on the thieves who steal elections" instead of "scapegoating the Greens," a reference to the Green Party, the ticket he ran on in 2000.

"The Democrats ought to look themselves in the mirror and ask themselves why they have not been able to landslide the worst Republican Party and the White House and Congress over the last 20 years," he said.

Nader said he does not believe that any of the candidates, including McCain, will come through on pledges to reduce the influence of special interests in Washington.

"First of all, if they wanted to do that, they'd put front and center public funding of public campaigns," cracking down on corporate crimes and other issues. "Washington has closed its doors on citizen groups," he complained, calling the nation's capital "corporate-occupied territory."

"We have to give the system more competition, more voices, more choices, more freedom, more diversity," Nader said in a defense of his candidacy. E-mail to a friend

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