Paying for sex is to be banned in Northern Ireland after Stormont Assembly members backed the move in a landmark late-night vote.

The proposal to outlaw purchasing sex is 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 soliciting, 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 Human Trafficking and Exploitation Bill was tabled before the Assembly by Democratic Unionist peer Maurice 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 Féin's decision to back the prohibition along with the DUP proving crucial.

The clause was passed during the bill's consideration stage by 81 votes to ten shortly after 11.30pm.

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 significant majority 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 the marathon debate.

Advocates of the ban insist it will reduce human trafficking in the region while critics claim it will merely drive the problem further underground.

Ruhama, the organisation supporting women in the sex industry, welcomed the move but said there are concerns the proposed ban will have a negative impact in the Republic with sex buyers moving south of the border.

Geraldine Rowley of Ruhama said the agency is calling on Minister for Justice Frances Fitzgerald to follow suit with similar legislation, adding that it will bring an end to some organised crime.

"The majority of the sex trade in Ireland today is run by organised criminal gangs, even the women we know who are trying to remain independent are telling us that they are finding it very, very difficult."

She said the legislation in the North is "calling buyers to account and we hope we will have it in the south."