A US judge has ordered the halt to an email campaign by the operators of adult websites after complaints by the FTC and Department of Justice that the email messages violated an anti-spam law.

Affiliates of ATM Global Systems, operator of adult websites including Sexyfriendsearch.com and Funhookups.com, sent out unsolicited email with false or misleading header information, and failed to include an opt-out mechanism and a valid postal address, all violations of US law, the FTC said in a press release on Tuesday.

A May 2 order from the US District Court for the Northern District of Illinois, Eastern Division, bars the company and owners Mark Richman and Nathaniel Seidman from further violations of the US CAN-SPAM Act. It also requires the company to establish an affiliate monitoring program and imposes a $75,000 (£37,500) civil penalty, the FTC said.

A representative of ATM Global Systems didn't immediately return a phone message seeking comment on the court order.

The company, based in Boca Raton, Florida, has used affiliates to drive users to its websites since January 2006 or earlier, the FTC said. The affiliates, paid commissions for referrals who signed up as members of the websites, sent spam with "lurid" subject lines, the agency said.

The email messages included false header information, making it difficult for recipients to determine the identity of the sender, the FTC said.

The judge's order included a civil penalty of $442,900 (£221,000) - the amount the defendants made from the spamming operation - and all but $75,000 (£37,500) was suspended, based on the defendants' ability to pay, the FTC said. If the court finds the defendants misrepresented their financial status, the rest of the penalty will be due.