His demand that the other Democratic candidates refuse and return campaign contributions directly confronts party front-runner Sen. Hillary Clinton who has received thousands of dollars from News Corp. executives.

"The time has come for Democrats to stop pretending to be friends with the very people who demonize the Democratic Party," said Edwards, who has ranked third in polls among Democrats behind Clinton and Sen. Barack Obama of Illinois.  "News Corp.'s purchase of the Dow Jones Co. and the Wall Street Journal should be the last straw when it comes to media consolidation."

Senator Clinton has received $4,600 from News Corp.'s President and Chief Operating Officer Peter Chernin and the same amount from Gary Ginsberg, the company's executive vice president of corporate affairs, according to donation records.

She also received $3,450 from James Murdoch, the son of News Corp. Chairman Rupert Murdoch. Last year the media patriarch, widely viewed as a conservative, held a fund raiser for Clinton's Senate re-election bid, raising questions about his political allegiances.

Edwards has been a fierce critic of News Corp. because he says its Fox News cable channel has a conservative tilt and has covered Democrats in an unfair manner -- a charge the network has denied.

The former senator from North Carolina refused to participate in a debate co-hosted by Fox that was to be held this month and other Democrats bowed out as well.

Sen. Chris Dodd, a Connecticut Democrat who is also running for president and who has criticized the deal, received a $2,100 contribution from Chernin. He has trailed in opinion polls, registering only in the single digits.

A spokesman for News Corp. declined to comment. The company proposed acquiring Dow Jones & Co. Inc., the parent of the storied Wall Street Journal financial newspaper, for about $5.6 billion including debt.