WASHINGTON (Reuters) - A bill aimed at limiting that unwanted junk e-mail known as "spam" was approved and sent to the floor by the Senate Commerce Committee on Friday with unanimous support from Democrats and Republicans.

It would strengthen the Federal Trade Commission's enforcement authority by allowing it to impose fines of up to $10 per e-mail on e-mails that violate existing laws against spam -- with a cap of $500,000.

Sen. Conrad Burns, a Montana Republican and co-sponsor of the legislation, said the bill would help both e-commerce and consumers burdened by unsolicited junk or pornographic e-mails.

"Rampant pornography and fraudulent credit deals were never the destiny of the Internet, but they have become commonplace fixtures in in-boxes everywhere," he said.

No similar measure is pending in the U.S. House of Representatives.

New Mexico Republican Rep. Heather Wilson's bill requiring spammers use a legitimate return address, so unwanted e-mail can more easily be blocked, has not yet been scheduled for a vote.

Twenty-two states have passed anti-spam legislation.

Spam has especially been a problem for rural consumers, many of whom pay long-distance charges for Internet connections and waste time and money erasing their unwanted e-mails, Burns said.

BOXER AMENDMENT

The Senate Commerce Committee on Friday approved an amendment by Sen. Barbara Boxer, a California Democrat, that would prohibit transmitting unwanted e-mails to addresses that were illegally obtained from Web sites.

Co-sponsor Sen. Ron Wyden, an Oregon Democrat, said moving the bill would help the FTC deal with thousands of complaints it has received about spam.

"The problem is, the technology is on the side of the spammer," he said.

The proposal would also require e-marketers to include a working return address to allow recipients the option of refusing further e-mails, and give Internet service providers the ability to bring suit to keep unlawful spam off their networks.

And, it would subject spammers who intentionally disguise their identities to misdemeanor criminal penalties.