Updated from 2:26 p.m. EDT

An awkward conference call with investors Wednesday afternoon proved a weak defense for

Omnicom's

(OMC) - Get Report

stock.

The company initiated the midafternoon call and issued a series of press releases after an article in

The Wall Street Journal

flattened the advertising conglomerate's stock. The company vigorously defended its practices, but investors, wearied by the twists and turns of accounting debates at companies such as

Tyco

,

Enron

and

Adelphia

, appeared eager to shut the door on the entire matter.

Omnicom shares dropped $15.28, or nearly 20%, to close at $62.28 -- improved from a 33.6% decline on Wednesday morning but not wildly improved over where the stock was trading at the outset of the call.

On the agenda was the

Journal's

lengthy article Wednesday morning suggesting that Omnicom's accounting for its many acquisitions made its growth look better than it really was. The article also contended that the departure of two board members this year came partly in protest of Omnicom's bookkeeping and disclosures, including issues related to the company's transactions with an entity holding a number of investments in Internet-related companies.

In a conference call punctuated by more than the usual number of bad connections and long pauses between analysts' questions, Omnicom CEO John Wren insisted the article contained no damaging revelations. "The only thing that is new is innuendo," he said, "and, in some cases, I think the facts are skewed wrong."

Zero-Tolerance

But, says one short-seller of Omnicom's stock, given the numerous cases over the past year when easily dismissed bad news has snowballed into financial crises for other companies -- especially those that, like Omnicom, have made numerous acquisitions -- Wren is fighting a difficult battle.

"We're in a zero-tolerance environment," says the short-seller, speaking on condition of anonymity. "It's probably going to happen to a few more companies."

While giving no indication he believed that Omnicom's accounting was misleading, the short-seller says recent history indicates that companies don't quickly overcome accounting-related bad news. "There's never one inning to these things. There's never one layer to these things," he says.

But Wren and Omnicom Chief Financial Officer Randy Weisenburger tried their best to put out the fire, addressing the

Journal

article broadly, then answering specific questions from analysts.

"Is Omnicom being managed and governed appropriately? The answer is yes," said Wren. The company's financial and accounting principles paint an accurate picture of the company, he said. Seneca, a partnership (discussed in the

Journal

article) to which Omnicom contributed its minority stakes in money-losing Internet companies, "was not financial engineering," Wren said. Among mangement at Omnicom, he said, "there is no turmoil or dissent."

Say Cheese

Among other complaints about the article, Wren and Weisenburger said it had used misleading snapshots of the company's cash flows. Weisenburger also disputed the paper's assertion that Omnicom's method of calculating how much of its growth is organic, as opposed to how much comes from acquisition, is more forgiving than the methods used by the rival advertising conglomerates

Interpublic Group

(IPG) - Get Report

and

WPP Group

(WPPGY)

. Asked whether Omnicom would report organic growth by the other companies' definitions, Weisenburger replied, "Frankly, I can't make sense of what they've said, and the numbers."

Apologizing for the performance of Omnicom's stock, Weisenburger said the company had tried over the years to be as open as possible and give as much information as it could. "We actually thought we were reasonably good at it," he said.

But he also said that because Omnicom must compete with other companies for acquisitions and new business, the company could hurt itself by putting too much information out in the open where rivals could take advantage of it. "I don't think it's really in shareholders' best interests to undermine that position," Weisenburger said.

Following the call, the Omnicom's board continued the defense. "There is no controversy on the Board," read a statement attributed to the board. "We fully support the Company's strategy, and are confident in its operating results, accounting practices and financial disclosures."