Campaigners have staged a demonstration outside Parliament against changes to pornography regulations.
Protesters gathered in London to oppose the decision to ban various sex acts from UK-filmed online porn videos.
Paid-for online porn videos must now adhere to the same rules as content produced for sex shop-type videos.
Protest organiser Charlotte Rose said the "ludicrous" restrictions were a threat to freedom of expression.
The 2014 Audiovisual Media Services Regulation, which the government says will crack down on "harmful content", came into effect earlier this month.
It means acts that would not be classified as an R18 rating, in line with guidelines laid out by the British Board of Film Classification (BBFC), are prohibited.
Practices now reported to be outlawed include spanking and strangulation. Protesters say some acts that show women enjoying sex are now banned while similar restrictions do not apply to men.
Critics argue the change not only damages the country's porn industry, with online viewers still able to access content banned in the UK by watching videos filmed abroad, but amounts to "arbitrary censorship".
About 20 couples took part in Friday's protest at the new regulations.
Ms Rose, a sex worker who stood for Parliament in the recent Clacton and Rochester and Strood by-elections, said the activities had been added to the list without the public being made aware.
"They've done this without public knowledge and without public consent," she said.
"There are activities on that list that may be deemed sexist, but it's not just about sexism, it's about censorship. What the government is doing is taking our personal liberties away without our permissions."
'Tried and tested'
Isabel Dean, a fetishist from London, said the restrictions were affecting people's livelihoods. "It's a farcical thing to breach people's basic rights to explore their sexual freedom, and it's just so limiting to UK producers and performers," she said.
"Small independent dominatrixes, anything with any sort of kink in their work - if you're working for yourself, producing your own clips, your own website, it's really damaging. Some people have had to close down sites that they've been working on for years."
Earlier this week, Lib Dem MP Julian Huppert called for a debate on the new regulations, saying the government should not be preventing adults from viewing legal and consensual sex.
The regulations were implemented without parliamentary debate because they transpose existing laws on to the online world, rather than create new legislation.
A spokesman for the Department for Culture, Media and Sport said: "The legislation provides the same level of protection to the online world that exists on the High Street in relation to the sale of physical DVDs.
"In a converging media world these provisions must be coherent and the BBFC classification regime is a tried and tested system of what content is regarded as harmful for minors."