Seventy-two House Democrats sent a letter to Federal Communications Commission Chairman Julius Genachowski on Thursday urging the commission to "avoid tentative conclusions which favor government regulation" when crafting new open-Internet rules.

The letter is one of many flying at the commission in advance of its scheduled vote next week on the "net neutrality" proposal.

The rules would prevent Internet companies such as Comcast Corp. (CMCSA), Verizon Communications Inc. (VZ) and AT&T Inc. (T) from selectively blocking or slowing certain Web content and would require providers to disclose how they manage their networks.

The letter, spearheaded by Rep. Gregory Meeks, D-N.Y., points to the "growth and innovation" in new Internet applications that has occurred under the current regulatory regime, "as compared with limited evidence demonstrating any tangible harm."

"We remain suspicious of conclusions based on slogans rather than substance and of policies that restrict and inhibit the very innovation and growth we all seek to achieve," the letter said.

A draft of the proposal is circulating among the five commissioners. It isn't public, but rumors about its content have sparked a flood of lobbying from concerned telecom companies on Capitol Hill.

Internet service providers are concerned that the rules would apply only to them and not other Web companies like Google Inc. (GOOG).

Manufacturers such as Cisco Systems Inc. (CSCO) and Motorola Inc. (MOT) are worried that the rules would hamper their ability to find new ways to manage Internet traffic.

Genachowski has said the rules will allow ISPs to manage their networks to ensure smooth performance during peak traffic times. He has also promised that the analysis undertaken by the FCC will be data-driven and fact-based.

-By Fawn Johnson, Dow Jones Newswires; 202-862-9263; fawn.johnson@dowjones.com