OUSTON, Nov. 5 — The latest set of asset sales by the El Paso Corporation, one of the nation's largest energy companies, is drawing a fresh round of criticism from experts, who say that the deals raise troubling conflicts of interest.

In two big transactions earlier this year, the company agreed to sell more than $1.5 billion in pipelines and other property to another publicly traded company that it created and controls, El Paso Energy Partners, L.P.

El Paso executives say that the deals are entirely proper and call them a "win-win" for both companies, which share an address here in Houston, a telephone number and some of the same employees and board members. El Paso will be able to raise cash by selling assets without giving up control of them. El Paso Energy receives solid assets that generate cash it can distribute to its unit holders. And all of this, the companies say, is out in the open, visible for investors to judge.

But a growing number of analysts find the deals troubling. A year after off-the-books partnerships helped topple Enron and sent the energy industry into a tailspin, the critics wonder why El Paso continues to transact such large deals with a closely held affiliate. They note that El Paso — as the general partner of El Paso Energy Partners and the owner of 27 percent of the partnership — controls, operates and profits from the assets it is selling.

"These are completely artificial transactions," said Kurt Wulff, an energy analyst at McDep Associates in Boston. "These are like deals within a family. And in many ways, the parent can make these deals come out the way they want them to."

In a report released on Monday, Moody's Investors Service also questioned the deals. The report expressed concern about whether El Paso Energy and other master limited partnerships in the energy industries were independent enough from their parents to negotiate fair prices in transactions. Indeed, Moody's said investors might need to regard the parents and their partnership offspring as single entities to fully understand the credit risks.

"We're looking at whether or not these entities ought to be consolidated from a credit point of view," said John Diaz, a managing director of Moody's energy group. In El Paso's case, consolidating the partnership's debt would send billions of dollars in liabilities back onto the parent's balance sheet.

The El Paso companies reject the suggestion that anything is amiss in their dealings. "We are proud of our association with El Paso Corporation," said Robert G. Phillips, a former El Paso executive who is chairman and chief executive of El Paso Energy, in a recent conference call with analysts. "We will continue to benefit from that relationship."

The companies, which declined to be interviewed about their dealings, have noted in public statements that a special committee of El Paso Energy's board was set up to review the deals between them. A financial adviser to the committee also reviews the deals for fairness. Both the conflicts and the deals themselves, the companies add, have been fully disclosed to investors.

In addition, the El Paso companies have taken steps to shore up their standing with Wall Street. To meet new requirements by the New York Stock Exchange for director independence, three El Paso executives, including the chief executive, William A. Wise, stepped down from the board of El Paso Energy Partners a few weeks ago. The partnership will replace them with outside directors.

Most Wall Street analysts also defend the deals, saying the prices seemed fair. "There are reports that say these corporations are forcing their partnerships to buy these assets. I would disagree with that," said John Tysseland of Raymond James & Associates. "Every transaction has been fair. I look at the prices on a historical level."

Still, criticism of El Paso — long a favorite of energy analysts — has grown in the wake of Enron's collapse. The company was sharply assailed earlier this year for its growing reliance on a series of deals with off-balance-sheet partnerships. Those deals let El Paso book hundreds of millions in profits years before they will be realized while keeping billions in debt off the books.

The pressure from investors, who have driven El Paso's stock price down around 80 percent this year, prompted the company to announce it would pull about $2 billion in debt back onto its books early next year. Now, though, investors have begun to realize that the deals with El Paso Energy Partners are pushing nearly as much debt back off the books.

Master limited partnerships give their investors a direct ownership interest in a group of assets. They were first allowed in the 1980's, but their use in the energy sector boomed in the late 90's, when Kinder Morgan Energy Partners, L.P. was created by Richard Kinder, a former Enron executive.

The partnerships receive special tax breaks and they are required to distribute the majority of their income in the form of quarterly, dividend-like distributions. Many, to attract investors, distribute as much as 80 or 90 percent of their income.

The partnerships often buy relatively stable energy assets like pipelines that generate steady cash flows. Many of them grow, and thereby increase their payouts, through acquisitions.

El Paso Energy Partners was formed in 1993, but did not make major acquisitions until the late 90's. In 1999, 2000 and 2001, it acquired a total of about $700 million in assets from the El Paso Corporation.

The pace of deal making picked up this year. In February, El Paso Energy agreed to acquire $750 million worth of natural gas pipeline and transportation assets in Texas and New Mexico from El Paso. And in July, the partnership agreed to acquire natural gas transportation equipment in the San Juan Basin of New Mexico, along with other El Paso property, for $782 million.

Under the terms of its various deals with the partnership, El Paso continues to manage and operate the assets for a management fee that is expected to reach $60 million this year. El Paso, which owns 27 percent of the partnership, also collects nearly 40 percent of the partnership's profits. Since 2000, it has received about $130 million of the $300 million in profits, according to analysts.

Indeed, one of the criticisms of the arrangements between the two companies is that, like other energy master limited partnerships, El Paso's is set up so that the company, as general partner, receives a bigger share of the profits as the partnership grows. Limited partners — that is, outside investors — in turn receive gradually smaller shares. Mr. Wulff at McDep Associates has warned investors away from investing in El Paso Energy Partners for just that reason. "The general partners are taking an exploding percentage of the profits," he said. "You put money into a hedge fund, and they want 20 percent of the profits. But in these partnerships, they say we want 2 percent at the beginning, then they get 20 percent, then 50 percent. This is out of proportion."

Other investors seem wary too. El Paso Energy had planned to raise more than $700 million to buy the San Juan Basin assets from El Paso, in part by issuing so-called "I-shares," or institutional equity. But last month, the company postponed the offering because of slack demand.

In an earnings release on Oct. 21, the company said it is determined "to proceed with the acquisition of the San Juan assets and is evaluating alternative sources of equity financing."

The problems with investors have arisen even though El Paso Energy has been a much better investment than El Paso and other conventional energy companies in the post-Enron energy stock decline. Supported by its strong distributions, El Paso Energy shares have fallen less than 20 percent in the last year.

Whether that relative outperformance continues, the questions about energy companies and their master limited partnerships are intense and investors are being cautioned.

"We put a report out to basically say, `buyer beware,' " Mr. Diaz of Moody's noted, referring to this week's report on master limited partnerships in the energy industry.