WASHINGTON (Reuters) - Antitrust authorities at the U.S. Justice Department on Thursday warned regulators against imposing “network neutrality” regulations that would bar broadband Internet service companies from charging extra to some content providers.

In comments submitted to the Federal Communications Commission, the department said some net neutrality proposals “could deter broadband Internet providers from upgrading and expanding their networks to reach more Americans.”

“Regulators should be careful not to impose regulations that could limit consumer choice and investment in broadband facilities,” the department’s antitrust chief, Thomas Barnett, said in a statement.

The concept of net neutrality is being studied by the FCC and has been the subject of much debate in Congress. Some lawmakers tried unsuccessfully to get net neutrality legislation passed last year.

Network neutrality proposals, backed by Internet content companies like Google Inc and eBay Inc, would bar Internet providers from charging extra fees to guarantee access to the Internet or give priority to some content.

However, the idea has been staunchly opposed by high-speed Internet providers such as AT&T Inc and Verizon Communications Inc.

Companies like eBay and Google worry that AT&T and Verizon will charge them more to get access to consumers or make it harder for consumers to get access to unaffiliated content.

The network providers counter that they would not block access to public Internet sites but want to offer private Internet-based services with faster speeds for uses such as downloading movies.

Last year, the FCC approved AT&T’s purchase of BellSouth Corp after AT&T promised to maintain net neutrality of its high-speed Internet platform for two years. It was one of several key concessions that AT&T made to ease concerns about competition.

The comments from the Justice Department come on the heels of a report in June by antitrust experts at the Federal Trade Commission that expressed similar views and recommended that regulators “proceed with caution” on any such proposals.

The department said proponents of the Internet regulation had failed to show that many consumers had been harmed in a way that would justify government intervention.

It said there was nothing unusual about the practice of setting different levels of service and pricing, citing as an example the various mail options offered by the U.S. Postal Service.

“These differentiated products respond to market demand and expand consumers’ choice,” the department said.

Advocates of the network neutrality idea criticized the department’s conclusions, saying regulations were needed because many consumers had little or no choice of broadband providers.

“This lack of competition and consumer choice for broadband access is the reason why (we support) preemptive safeguards to ensure that cable and telephone companies do not destroy the Internet as we know it,” said the Open Internet Coalition, a group comprised of consumer groups and Internet content companies such as Google.

On the other hand, the department’s comments were met with praise from AT&T.

“We continue to urge policymakers to focus on the real issue of the broadband era, which is to promote the benefits of broadband services at affordable rates for all consumers,” AT&T said in a statement.