Britain fined online porn company AVS Group £1 million on Thursday for not having robust age checks in place to protect children, the biggest penalty imposed to date under its new online safety regime.

Media regulator Ofcom said it fined the operator of 18 adult websites for lapses relating to age checks plus an extra £50,000 for failing to respond to information requests.

Reuters could not contact AVS, which Ofcom said was registered in Belize, for comment.

The Online Safety Act is designed to protect children and vulnerable users from illegal content online and came into force this year, but has caused tensions between U.S. tech companies and Britain.

Critics of the law have said it threatens free speech and targets U.S. companies. This is the third company Ofcom has fined under the new regime. The first was U.S. internet forum site 4chan in October, for 20,000 pounds.

4chan filed a legal case against Ofcom in August, saying its enforcement violated Americans’ right to freedom of speech.

THREE-QUARTERS OF ONLINE PORN BEHIND AGE CHECKS

Ofcom said it started looking at AVS in July as part of an investigation into dozens of adult sites.

Oliver Griffiths, Ofcom’s Online Safety Group Director, said AVS was a significant operator, with about 2.5 million British users across its 18 sites in October.

“They did have a form of age check in place, but it wasn’t good enough, and that’s why we’ve taken it through to a fine,” he said in an interview.

The penalty AVS faces could increase by 1,000 pounds a day if effective age checks are not brought in within 72 hours, Ofcom said.

Griffiths said Ofcom had worked with the porn industry to help providers comply with the new law.

“There’s no other equivalent country that has got as much porn traffic behind age checks; it’s about three quarters of the total volume,” he said.

“We’ve seen visits to sites drop by about a third, and we’ll be interrogating the data to check how much of that is actually from children.”