Rogue landlords are exploiting vulnerable people by offering free accommodation in exchange for sex, charities have warned.
They say the deals take advantage of those unable to afford spiralling rents and "go as close to the edge of the law ... without breaking [it]," according to Daily Mail.
Websites hosting adverts for such offers are being urged to tackle the problem.
As young people and the low-paid are priced out of accommodation, particularly in south-east England, "sex for rent" adverts have sprung up online.
One classified advertising site, Craigslist, carried more than 100 such listings in a single day, a BBC investigation found.
A female student who answered one of them said she felt it was her only option.
She added: "He took me into his living room, got me drinks, and then after that it was just straight upstairs ... He would do what he wanted, forcefully, and I just sort of went along with it."
Labour MP Peter Kyle said classified websites should stop allowing the adverts or Parliament should intervene.
"If [websites] don't stand up to this and then accept their responsibility, I will be pushing for legislation to do it for them," he said.
A string of charities have backed his calls for a crackdown.
Mel Potter, of the Brighton Oasis Project for women, said: "It's something that potentially can trap someone and put them at risk of violence and abuse."
Andrew Wallis, of anti-slavery charity Unseen, added: "I think these adverts go as close to the edge of the law that they possibly can without breaking the law.
"The [landlords] would argue [tenants] have chosen voluntarily to enter that situation. The trouble is when you have a vulnerable person who then becomes exploited, the concept of choice soon disappears."
Paul Noblet, of homeless charity Centrepoint, called for advertising sites to consider a "voluntary code" under which the offending posts could be removed.
One of the adverts on Craigslist, from the owner of a "small two-bedroom house near Hull", says: "Money is not an issue, I would prefer some company.
"There are some stipulations to the living arrangements ... This would be a mutual benefits arrangement. Free rent, paid in other methods."
Meanwhile, a "City worker" living in a "luxurious spacious apartment" in central London was seeking "a dominant attractive woman who in return will place me beneath her beautiful feet and boss me around".
The 35-year-old asked anyone interested to send photos of themselves and their "lovely feet".
Other adverts included a man in Maidstone, Kent, seeking a woman to move in and pretend to be his girlfriend.
A double room in Rochester, Kent, was said to be available in exchange for unspecified "services", while younger men were targeted by a post from a Brighton property owner.
An "open-minded naughty sexy girl" was requested by a London landlord, who added: "Send your pictures, age, name, maybe nationality ... Room can be used to work from like massage etc or just to live in."
One landlord told the BBC: "I was thinking once a week, something like that, I'm happy as long as there's sex involved."
Another said: "As far as the apartment's concerned, it's as if we're flatmates. It's all the bills, the rent, free."
But he added: "You agree sort of like a couple of times a week, pop into my room sort of thing."
A landlord who defended the arrangement as a "friend with benefits" situation, added: "You can argue that high rent charged by landlords is taking advantage too.
"There's no compulsion for them to do this. Everyone goes into it with their eyes wide open. I am the last type of person who'd like to take advantage. Both sides have something the other person wants. I see it as a win-win situation."
He rejected claims it could be construed as sexual exploitation, saying that people working in jobs they did not enjoy was "like a form of prostitution".
Craigslist did not respond to requests for comment.