One man and three women have been arrested in a police operation which could lead to the first prosecution under a Northern Ireland law that criminalises the purchase of sex.

The Human Trafficking and Exploitation Act 2015, which came into force in June, was inspired by sex work laws in Sweden and Norway.

DUP peer Lord Morrow, who introduced the bill, said it would “make a difference for the victims of this despicable trade” by creating offences that only relate to the purchase, rather than sale, of sex.

The Chief Constable of the Police Service of Northern Ireland, George Hamilton, told the PSNI policing board that a man had been detained for “paying for sexual services” in an alleged brothel last month.

However, the police operation attracted controversy after he admitted three women were also arrested under the charge of “keeping a brothel”.

Dublin solicitor Wendy Lyon, who specialises in sexual, reproductive and maternity rights, told Irish Legal News: “The sale of sexual services is not an offence under the Human Trafficking and Exploitation Act 2015; however, prior legislation on ‘brothel keeping’ remains in force.

“In the Republic, legislation has also been introduced to criminalise paying for sex. Minister for Justice and Equality Frances Fitzgerald has told the Oireachtas she has no plans to change the brothel keeping law, although in both jurisdictions it means that people who sell sex - who are theoretically ‘decriminalised’ under the proposed law - can be arrested for working together.”