To the unaware, the true meaning of some of the phrases used on the ads for tenants could be missed. Rooms for rent are offered in exchange for “benefits” or “keeping me company”. Others are less subtle – “free accommodation in exchange for an erotic arrangement”.

Renting rooms for sexual favours is seen as a growing menace by campaigners, and a byproduct of a housing crisis where young people are unable to find somewhere to live without spending exorbitant sums.

The problem has become particularly marked in university towns, where young women are targeted by rogue landlords. But while then justice secretary David Lidington last year said such offers may breach the Sexual Offences Act, there is frustration that more is not being done.

“Since last year, there has not been a single arrest, let alone a conviction, let alone anybody actually going to jail for it,” says Peter Kyle, Labour MP for Hove.

Kyle has been campaigning on the issue and has consistently called for landlords who offer accommodation in exchange for sex to be prosecuted.

Room for ‘favours’

The offending adverts typically offer free room or bed share in exchange for “intimacy”, “benefits” or “fwb” – friends with benefits. While many appear in London, room shares in exchange for sex are advertised around the country through sites such as Craigslist.

“Free accommodation for attractive female (Central London)” reads one of a selection from Craigslist. “Maisonette share, very low cost, with Dominant strict gentleman S London”, says another posting. “Room available for homeless woman (North London/Essex)”, reads a further ad.

One landlord claims to be a 35-year-old professional, “posting the ad to see if any lady would be interested in free accommodation in exchange for an erotic arrangement”. His ideal tenant would be “an attractive girl. Sex is, of course, what I’m proposing ... but look ... we have to like each other and have some chemistry.”

A broken system

Campaigners for fair housing have said the “sex for rent” ads have come about as a result of a dysfunctional housing market.

“Some people are desperate for housing. Others have the power to exploit that,” says Kate Webb, head of policy at Shelter, the homeless charity.

This was grimly illustrated in a survey carried out last year where people detailed their experiences. One woman told how a landlord wanted to have sex with her in return for keeping the rent down – while her six-year-old daughter was in the garden. “He was asked to leave. He did. Damp was never fixed. Asthmatic kid still needed hospital.”

Another told of how she received a text from the landlord after a viewing saying she could have the flat for free if she performed some “very explicit sexual acts with him”, even though she is gay and had visited with her wife.

Another woman, who was struggling to pay the rent one month, was thrown out when she refused to provide sex.

Paul Noblet, head of public affairs at Centrepoint, says thousands of young people are taking desperate measures to get off the streets. He is calling on the government and police to enforce the law.

“If the government is serious about ending the crisis of youth homelessness, it must build more genuinely affordable homes and provide sufficient funding for homelessness services.”

The law

The Ministry of Justice has previously said that offering accommodation in exchange for sex is inciting prostitution, an offence which can carry a sentence of up to seven years in jail.

Katie Russell, of Rape Crisis England & Wales, says the Sexual Offences Act defines sexual consent as when an individual “agrees by choice and has the freedom and capacity to make that choice”.

“Agreeing to have sex with someone under the pressure and fear of homelessness, or in exchange for the basic right to have somewhere to live, does not equate to agreeing by choice,” she says. “Any sexual activity without consent is a very serious sexual offence.”

Prosecutions are difficult as many women, especially female rough sleepers or those trapped in abusive relationships, are unlikely to go to the police, but websites do have the power to act, says Webb. She welcomed last year’s statement from the Ministry of Justice to stop the crime becoming normalised. “It was important to state that this is not legal, it is not acceptable, to stop it from snowballing.”

However, Kyle has become frustrated at the lack of prosecutions in the area. “We do not necessarily need new laws, I just want to see the existing ones applied. Advertising in this way is not against the law – only the actual transaction is. This makes prosecution difficult.”

Some police are hesitant to commit large resources to the problem in cases which may not secure a conviction, he adds.

The other victims

While much of the attention is focused on women being exploited, vulnerable young men are also targeted.

Men can fall to the bottom of the local authority housing list, as they are seen as less at risk than women, says Duncan Craig, chief executive of Survivors Manchester, which supports male survivors of sexual abuse and rape. “If you are sleeping on the streets and a stranger offers you a warm room, a comfortable bed and a shower, the temptation may be too great.”

When contacted by the Observer, Craigslist did not respond to questions. A spokesperson for Gumtree, where the Observer found an ad that was subsequently made unavailable, says it has systems to block similar posts.

“We do not tolerate these types of advert on Gumtree. We have a variety of measures in place to ensure they do not make it on to the platform, and work closely with law enforcement agencies to share information.

“We have met with Peter Kyle to discuss this important issue and provide reassurance that Gumtree does – and will continue to – remain compliant with the law. We work hard to ensure Gumtree is a safe place to find tenants or a place to live,” it says.

Kyle has welcomed the moves by Gumtree, which he describes as proactive in trying to resolve the problem. Craigslist, however, comes in for severe criticism. “It has not returned my calls, or responded to letters written on parliamentary paper ... I cannot stress [enough] how disgusted I am with them.”

A number of the ads found by the Observer on Craigslist were subsequently removed, apparently after being flagged by users.

What the ads say

‘I have a spare room for someone who likes to get naked at home. Send naked pic and details if interested.’

‘I’m offering free temporary accommodation for nice, kind and tidy lady in exchange for cooking, cleaning, and keeping me company’

‘Room for a female guest only. Temporary for two weeks and free if you are willing to do the cleaning etc.’

‘Room for homeless woman. Rent free and food provided. Any race welcome.’

‘Female of any age to share room. King-size bed. I don’t want payment. Just company. Nothing sexual unless we both want it.’

‘A fresh start rent free. Local small business owner. Employment if wanted. Wanting a woman for long-term friendship.’

‘Free accommodation and bills for a woman in exchange for house work and fb/fwb. House mate only home two to three days a week due to work. Please send picture and description.’

‘I am looking for a female tenant … I would offer a suggestion of a different arrangement instead of money, but I am happy either way.’