There are fears that ISPs could become the web's gatekeepers

The agency said it was opposed to "network neutrality", the idea that all data on the net is treated equally.

The comments put the agency at odds with companies such as Microsoft and Google, who have called for legislation to guarantee equal access to the net.

The agency submitted its comments to the Federal Communications Commission, which is investigating net access.

Several US internet service providers (ISPs), including AT&T and Verizon, have previously said that they want to charge some users more money for certain content.

This has particularly become an issue with the rise of TV and film download services.

A similar debate is ongoing in the UK.

One web

The Justice Department said imposing net neutrality regulations could hinder development of the internet and prevent ISPs from upgrading networks.

The agency said it could also shift the "entire burden of implementing costly network expansions and improvements onto consumers".

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

The agency's stance is contrary to much of the internet community that believes in an open model for the internet.

Net neutrality advocates argue that a two-tier internet would allow broadband providers to become gatekeepers to the web's content.

Providers that can pay will be able to get a commercial advantage over those that cannot, they say.

In particular, there is a fear that institutions like universities and charities would suffer.

Last year, Sir Tim Berners-Lee the inventor of the web rallied against the idea of a two-tier internet.

"What's very important from my point of view is that there is one web," he said.

"Anyone that tries to chop it into two will find that their piece looks very boring."