Despite new laws making it illegal to pay for sex, there remains plenty of men prepared to break the law to do it and exploit trafficked women.
And despite one local brothel pimp - who had been making a fortune exploiting sex workers - being exposed by a BBC Panorama programme, dozens more pimps continued to ply their trade in the housing estates and leafy suburbs of Ulster.
The sex seller, who the programme did not name, was exposed as running a number of brothels across Belfast during the hard-hitting documentary Online Pimps Exposed which revealed how pimps are using legitimate online platform Vivastreet to control and advertise sex.
The pimp told the BBC he had done nothing wrong, but he was filmed picking up girls from Dublin Airport and dropping them off at various locations in south Belfast and the city centre.
He was also seen visiting the properties, rented in his name, with cleaning equipment, bedding and other supplies just before he 'placed' sex workers in them.
The shocking documentary was also able to show how pimps are spending thousands of pounds on advertising girls on Vivastreet, a classified ads website being used to advertise sex workers and trafficked women.
All of the women advertise that they are working independently but many have been trafficked and are working for a local pimp.
You don't need an account for Vivastreet and users can browse women for sex as easily as they would browse for car insurance or a takeaway meal.
Undercover reporters posed as potential clients at several of his suspected brothels off the Lisburn Road and at another apartment just off Castle Street in the city centre.
The investigation found sex workers working in squalid conditions offering full sex and other sex acts for £70 per half hour.
The men set up these illegal encounters by using Vivastreet, which legally advertises everything you can imagine from cars to furniture.
Sex encounters can be arranged within minutes and despite the BBC Panorama expose there remained hundreds of women - and also men - selling sexual services all over Northern Ireland on the site.
A quick search on Thursday night found more than 150 sex workers available in Northern Ireland, though that number will likely double at the weekend.
This is despite legislation being brought into law in Northern Ireland six years ago making it a criminal act to pay for sex.
The Human Trafficking and Exploitation Act 2015, introduced here following Lord Maurice Morrow's Bill, includes a clause making the purchase of sexual services illegal.
If convicted, a person could be fined, sentenced to a maximum of one year's imprisonment, or both.
It remains an offence to keep or manage a brothel, but the new law removed criminality from soliciting in the street or public place.
Depressingly, during the investigation it was found there is no shortage of men prepared to take that risk and the sex workers we encountered on Vivastreet were just the tip of iceberg.
During secret filming, scores of men were seen coming and going from the properties, with the weekend being particularly busy.
After contacting sex workers through the Vivastreet platform, men are told to go to a particular area but are only told which property they will meet in seconds before the arranged appointment.
In one brothel an undercover reporter is seen to be offered sex and is also given the opportunity to pay for more than one sex worker at a time.
Another undercover reporter went to an arranged meeting at another of the pimp's seedy south Belfast brothels and a hidden camera actually picked up the pimp answering the door and ushering him to a bedroom upstairs where a woman was waiting.
Vivastreet told the BBC it was committed to eradicating any potential exploitation but there were calls from campaigners for women's rights for the practice of selling sex online to stop.
The website says providing a safe platform is its top priority.
The site has an established section for adult listings, and prostitution is legal in the UK as long as the sex workers are acting of their own free will.
However, acting as a pimp - exerting control over sex workers for financial gain - is not legal.
A Vivastreet spokesman has said:
"Providing a safe platform for legal, user-generated content is our top priority.
"We are committed to eradicating any potential exploitation from our site.
"We take any allegations of exploitation extremely seriously and have a range of stringent measures in place to detect criminality, remove bad actors and block users identified as high risk.
"This year alone, more than 29,000 ads have been rejected outright and not allowed on the site.
"Unfortunately, in common with other user platforms, a small minority will always seek to circumvent our rules.
"That’s why – unlike some other sites — we proactively report suspicious content to police forces around the country and assist with prosecutions and geo-block high risk countries.
"We have a partnership with the charity operating the UK-wide Modern Slavery &Exploitation Helpline and encourage all users to report any concerns about trafficking or exploitation to them.
"In addition, our staff this year received training from Stop the Traffik so they are alert to the signs of exploitation and know what steps to take if they suspect trafficking.
"For advertisers that fall into higher-risk groups, we use an independent verification system which includes phone, email and age checks.
"We welcome new online safety legislation and believe that safeguarding measures across the entire industry should be robust.
"That’s why we are working with the National Crime Agency and the Home Office to develop an industry-wide approach to preventing exploitation and online trafficking.
"We will continue to collaborate with sex worker charities and law enforcement precisely because we want to continuously strengthen the safety measures on our site.”
Panorama analysed data from the site and found that some of the adverts for sex contained the warning signs of sexual exploitation.
There have been numerous prosecutions of pimping and sex trafficking involving people who have used Vivastreet to advertise the women they are exploiting.
In one case in the north-west of England, a man - Catalin Mihailescu -- spent £25,000 placing adverts on Vivastreet in 2017. The website even gave him his own personal account manager.
Diana Johnson, chair of the All Party Parliamentary Group on Commercial Sexual Exploitation, told the programme it was time to get tougher with sites advertising sex for sale.
"Currently in the UK we are a pimp's paradise," said the Labour MP.
"Our laws in this country are out of date."
She added: "I think we need to look at those laws again and actually make them fit for purpose."