Donald Trump, the owner of the Miss Universe Organization, listens during a news conference announcing that Miss California USA, Carrie Prejean, would retain her title in New York May 12, 2009.[Agencies]

PHILADELPHIA - A New Jersey judge on Wednesday dismissed a lawsuit for defamation filed by Donald Trump against an author whose book gave an estimate of the real estate developer's wealth much lower than Trump's own.

Superior Court Judge Michele Fox rejected arguments by Trump's lawyers that he had been the victim of "actual malice" as a result of Timothy O'Brien's book "Trump Nation: The Art of Being the Donald" published in October 2005.

Reading her opinion from the bench in Camden, Fox also ruled that co-defendant Warner Books, part of Time Warner Inc, was not "vicariously liable," as Trump had argued, because O'Brien was an independent contractor.

"There is no agency relationship," Fox said in her opinion.

O'Brien, editor of The New York Times' Sunday business section, cited three confidential sources who estimated Trump's net worth at between $150 million and $250 million, much lower than Trump's own estimates of around $4 billion.

Fox said Trump had failed to prove that O'Brien knew the information from his sources to be false or had used the information recklessly.

"O'Brien reasonably believed they were accurate," the judge said in the opinion read to lawyers during a conference call.

Trump claimed his business and his reputation had been damaged by the book, which has sold about 17,000 copies. He told The Wall Street Journal in May that he was worth about $4 billion, down from an earlier estimate of $5 billion to $6 billion in early 2005.

Fox cited defense arguments that all three sources -- whose identities O'Brien declined to reveal, citing a law designed to protect journalists' sources -- had similar estimates of Trump's net worth. Fox noted that O'Brien had also included Trump's own estimate in the book but excluded the author's.

The plaintiffs contended that O'Brien did minimal investigation to support his claims, had a history of negative reporting about Trump, and ignored information provided by Trump's associates.

The judge declined to address the issue of damages, as the defendants had requested.