WASHINGTON (CNN) -- Companies sending unsolicited messages should be prohibited from trying to disguise the content or origin of their e-mail, the Federal Trade Commission recommended Tuesday.

The FTC made the proposal in a newly released report that laments hours and money wasted over downloading and eliminating so-called "spam," but stops short of calling for strong measures to relieve clogged e-mail boxes because of free-speech concerns.

A study on spam and spamming-related issues was put together by an ad hoc group that included major Internet companies, such as America Online and AT&T, and organizations whose members send junk e-mail.

Because the different groups couldn't agree, the report doesn't specify whether there ought to be new federal laws controlling junk e-mail.

The FTC's report describes hours wasted by people downloading and reading junk messages. The process can be costly for Internet users who pay hourly connection fees, and it's expensive for Internet providers to store and transmit those unwanted messages across their networks.

"If every business that was sending out unsolicited commercial e-mail had to hear back from all the 300,000 people they ... (made angry), and they had to bear the cost of that, folks would realize it's not the most effective means of getting your message out," said Deirdre Mulligan of the Washington-based Center for Democracy and Technology, which coordinated the report.

Some computer users have argued that legislation cannot solve the problem of clogged e-mail boxes and say individuals should use their software to protect themselves.

For example, a person can set up the latest software to automatically delete any message it finds containing specific words or phrases, or sent from certain companies. But if a company disguises its information, the filter is useless.

"It tends to be a cat-and-mouse game," said Jill Lesser, director of law and public policy for America Online. "Spammers do have mechanisms to allow them to get around our filters."

"Filters ... will really never be perfect," said Jason Catlett, president of Junkbusters Corp., a New Jersey company that fights unwanted e-mail.

"If you're taking your laptop to Paris and you have to download your e-mail over an expensive long-distance phone call, you still have to download that stuff even if it's junked before you see it. It's really sweeping the cost under the carpet."

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Lesser called the problem of junk e-mail "the single most widely received complaint from customers" at AOL, with more than 12 million subscribers. "People are furious about it," she said.

The FTC report's lack of a general condemnation of junk e-mail was upsetting to the Coalition Against Unsolicited Commercial e-mail, which supports a ban on the practice and participated in the study.

"The recommendations and conclusions in the report, we find are somewhat misleading in the way they seem to represent a consensus among the participants," said Ray Everett-Church, who co-founded the coalition. "The implication there was a broad consensus ... is just not correct."

AOL's Lesser said her company is "very comfortable" with the recommendations.