Soho prostitutes will be put in danger if a bill aimed at curbing sex trafficking becomes law, the English Collective of Prostitutes has warned.

Under the Policing and Crime Bill, read for the second time in the Commons on Monday receptionists and maids who look after the area's prostitutes could be prosecuted for 'controlling prostitution for gain'.

If it passes through Parliament unamended, the law will target demand for sex, making it illegal to pay for sex with a trafficked woman and eliminating the mitigation of not knowing the woman has been illegally brought into the country.

It will also make it easier to prosecute people-traffickers or pimps, who control the women for gain.

"We are worried that the police or local authorities may construe that as including maids, who help working girls," said a spokeswoman for the ECP.

"Women who are working in the safety of flats will be forced to work alone and will then be open to becoming victims of violence from punters and criminals."

The fears come a month after a receptionist - who cannot be named - working at a Soho flat used to sell sex, was handed a written notice by police, warning she could face charges for helping the prostitute.

The flat, one of an estimated 50 in the area, was visited by police to make sure trafficked women were not being forced to work.

None were found and charges were not brought against the receptionist, but the action has heightened concerns that the oldest profession in the world could soon become more difficult in Soho.

The ECP spokeswoman added: "The receptionist is a grandmother and has worked in Soho for 30 years.

Soho is one of the safest places for women in the sex industry to work. She is the first line of defence against violent attacks and exploitation. If the police are allowed to proceed against her, other receptionists will be driven away and women will be forced to work alone."

The Home Office says the new law is designed to protect women who have been trafficked to the UK for the sex trade.

Police estimate anywhere between 6,000 and 18,000 trafficked women and girls are be working in brothels across the UK.