The internet could soon have its own red light district after the ".xxx" suffix was approved – though pornography companies are not keen to use it.

Icann, the organisation which determines what "top-level domains" (TLDs) such as .com or .uk can be added to the internet announced today that it will begin the process of registering .xxx by making checks on ICM Registry, the company that wants to run the domain and sell registrations.

It marks the closing stages of a 10-year battle by ICM Registry, now run by the British internet entrepreneur Stuart Lawley, to get the .xxx domain set up so that legal pornography sites can be found in a single grouping.

Yet pornography is already plentiful online. One of the most valuable domains in the early days was sex.com, which was the object of a bitter battle in which rivals battled it out to own what was seen as a honeypot for surfers. In 2007 porn.com was sold for $12m.

But many pornography companies are unhappy with the idea of a dedicated space online because they expect that as soon as .xxx is implemented, conservative members of the US Congress will lobby to make any sex-related website re-register there and remove itself from other domains such as .com or .org.

That would mean that sex sites could be more easily filtered out from web searches, and lower their revenues. Free speech advocates also worry that sites about topics seen by US conservatives as controversial, such as homosexuality, might also be forced to use the .xxx suffix.

Icann acknowledged it had made mistakes in reversing its decision to accept ICM Registry's proposal three years ago under pressure from the Bush administration. Icann also said the proposal had been rejected because it lacked the backing of the pornography industry.

Lawley, who insists that child pornography will be banned in the domain space, thought the new address could easily attract at least 500,000 sites making it after ".mobi" the second biggest top-level domain name with a specific sponsor registrar.

The .mobi TLD, set up in 2005, was sponsored by a range of companies, including Google and Nokia, to create sites for browsing with mobile phones.

But where the .mobi TLD had commercial sponsors, the .xxx domain is notable for only having ICM Registry, which stands to benefit from every domain name it sells. Lawley says he expects to make $30m (£20m) a year in revenue by selling each .xxx site for $60, and pledges to donate $10 from each sale to child protection initiatives.