A law intended to criminalise men who use prostitutes has led to 43 convictions in England and Wales in its first year of operation.
Police say the law is difficult to enforce as it relies on women coming forward to give evidence of coercion.
The law, officially known as Section 53A of the 2003 Sexual Offences Act, is meant to reduce the number of men buying sex by striking fear in men lest unbeknown to them the sex worker has been coerced.
The law allows police to prosecute men who have sex with women even if they did not know the woman had been forced to work as a prostitute
Greater Manchester Deputy Chief Constable Simon Byrne, who is the Association of Chief Police Officers' lead on the issue of prostitution, said he was surprised at how many convictions there had been because the law is difficult to prosecute
Speaking to the PM programme on BBC Radio 4, Byrne said:
The whole law in relation to this particular part of policing is confusing. We are calling for a simplification.
We are looking at a range of options in dialogue with the Home Office to try and simplify things and to look at good models of practice in other parts of the world.
Acpo ludicrously claimed last year that at least 2,600 prostitutes working in brothels in England and Wales had been trafficked from abroad, almost one in 10 of the estimated 30,000 working prostitutes. But even after raiding 100's of brothels the police
can find hardly any trafficked women.
The figures are rightfully disputed by people working in the sex industry. They argue that most women are engaging in consensual sex, simply to earn money.
Niki Adams, from the English Collective of Prostitutes, says the law does not address the fundamental issues:
I don't think this law should be used at all. It undermines sex workers' safety and it targets the wrong people. It targets clients who may be involved in consenting sex rather than the rapists and traffickers who should be
targeted by the police.
Despite the police's call for clarity, the government told the BBC that it has no plans to change the law on prostitution.
Convictions under Section 53A of the Sexual Offences Act 2003 by area:
South West: 11
North East: 7
East Midlands: 2
West Midlands: 1