The Northern Ireland Office is seeking feedback on plans to allow prostitutes to work together at the same address to improve their personal safety.
At present a building where two or more prostitutes work is defined as a brothel.
The issue is contained in a consultation paper, but change to legislation has been strongly criticised by residents' groups and an Ulster Unionist Assembly member.
Esmond Birnie, whose constituency reportedly contains up to 50 houses where prostitutes work, said: "South Belfast already has dozens of brothels operating at any particular time in rented apartments and this has not reduced problems in relation to kerb-crawling in the area or indeed various immigration or trafficking abuses."
Referring to proposals for a new law for England and Wales, he added: "The government's recent proposal to allow two or three prostitutes and/or receptionist or maid to work together legally in brothels is not a solution to the many problems associated with south Belfast's expanding vice industry.
"There is no evidence that decriminalisation or tolerance of prostitution would achieve the objective of reducing exploitation, improving the safety of those involved and making resident communities safer."
The NIO consultation document states: "At present only one person may work as a prostitute; more than that and the premises are classed as a brothel and are therefore illegal. This runs counter to the advice that women should not work alone in the interest of safety."
It adds: "The government plans to bring forward proposals for an amendment to the definition of a brothel so that two [ or three] individuals may work together. We would propose to make similar amendment to the law in Northern Ireland."
A government spokesman denied the consultation was about easing restrictions on prostitution. The government wished to provide greater protection for those in the sex industry. The paper had "asked whether we should follow proposals for England and Wales to allow two or three women to work together from one address in the interest of their safety," the spokesman said.