The Human Trafficking and Exploitation Bill was tabled before the Assembly by Democratic Unionist peer Lord Morrow

A landmark ban on paying for sex in Northern Ireland has been hailed by Christian groups but denounced by prostitutes' representatives.

The region will become the first part of the UK to back such a clamp down after Stormont Assembly members supported the contentious move in a vote late last night.

The proposal to outlaw purchasing sex was among a number of clauses contained in a Bill aimed at amending Northern Ireland's laws on trafficking and prostitution.

Paid-for consensual sex is currently legal in Northern Ireland, though activities such as kerb crawling, brothel keeping and pimping are against the law.

A ban will see the region implement a prohibition similar to the model operating in Sweden.

The Evangelical Alliance in Northern Ireland praised the bill as a "significant step in the right direction".

However, a statement issued by sex workers said they were "devastated" and claimed the move would drive the trade further underground, making it more dangerous.

David Smyth, from the Evangelical Alliance NI said: "While no Bill is perfect, and legislation can only take us so far, this is a significant step in the right direction.

"This is 'unfinished business' for Christians, carrying on the work of William Wilberforce to this day."

He added: "Sadly, there are an estimated 29.8 million people in slavery today - more than were transported during the slave trade. Our hope is that this law will lead to Northern Ireland becoming a world leader in tackling human trafficking."

The statement issued by campaign group Ugly Mugs on behalf of Northern Ireland sex workers said: "This new bill will only drive sex work further underground and make it more dangerous for the most marginalised sex workers."

It added: "We ask the Northern Ireland Assembly to reconsider this law and look at the evidence. This law will not reduce trafficking and will make working conditions more unsafe."

The Human Trafficking and Exploitation Bill was tabled before the Assembly by Democratic Unionist peer Lord Morrow.

The fate of the Bill's contentious clause six, proposing the ban on purchasing sex, was uncertain at the outset of the debate, with Sinn Fein's decision to back the prohibition along with the DUP proving crucial.

In the end the clause was passed during the Bill's consideration stage by a significant majority of 81 votes to 10.

Stormont's Justice Minister David Ford, leader of the cross community Alliance Party, opposed the clause.

While the legislation still has to pass further Assembly stages, the sizeable support within the devolved administration means it is essentially now destined to become law.

Research published by Queen's University in Belfast last week said about 17,500 men pay for sex in Northern Ireland every year.

Sex workers opposing the clause and a trafficking victim in support of the ban were among those at Parliament Buildings in Belfast to watch yesterday's marathon debate.

An academic specialising in legislation affecting sex workers and their clients said the new law in Northern Ireland would "only exacerbate an already tenuous relationship between the sex work community and the police".

Dr Sarah Kingston, who is senior lecturer in Criminology at Lancaster University's Law School, said: "Its introduction ignores a wealth of research which indicates how the criminalisation of sex workers and their clients can push the industry underground, as they attempt to evade prosecution.

"Given that sex workers often face violence in their work, pushing the industry further underground will only increase the likelihood of its occurrence, as those who perpetrate violence know that sex workers and their clients will be reluctant to report to the police.

"Sex workers are already extremely reluctant to report rape, violence or sexual assaults to the police because they fear they will not be believed or that their case would not be pursued.

"The law will also contribute to the inherent stigma which is attached to sex workers and their clients. Research has highlighted that sex workers experience more severe forms of violence than non-working women, and are more likely to be murdered.

"Criminalising any aspect of prostitution-related activities will only contribute to the stigma associated with sex work."

Lord Morrow rejected claims that the law would be unenforceable. He said he anticipated the bill would become law in the middle of next year.

"This is not the final stage of its passage through the legislative process," said the peer.

"However, I now look forward to seeing it passed into law next year. It is legislation which can make a major difference to some of the most vulnerable people in our society. I am delighted that the Assembly voted so overwhelmingly in support of that principle, and when made aware of the problem did not simply choose to look the other way."