David Cameron has called for a clamp-down on kerb crawling and said the decriminalisation of prostitution should be "looked at again".
It comes as a large-scale police operation to try to find the bodies of two missing women who worked as prostitutes in Bradford continues.
Stephen Griffiths, 40, who is charged with murdering three women, appeared in court on Friday.
The English Collective of Prostitutes has called for a change in the law.
On Friday morning Mr Griffiths, of Thornton Road, Bradford, gave his name in Bradford Magistrates' Court as "the crossbow cannibal".
He is accused of murdering prostitutes Suzanne Blamires, Shelley Armitage, and Susan Rushworth.
Police found the remains of Ms Blamires, 36, in the River Aire on Tuesday, but as yet there have been no traces of Ms Rushworth, 43, and Ms Armitage, 31.
'Had to go'
Dozens of teams from West Yorkshire Police are searching a variety of locations across Bradford including around the city's red light district.
Speaking after Mr Griffiths appeared in court, Mr Cameron said the murders were a "terrible shock".
He said it was important not to "jump to conclusions" because decriminalisation would bring "all sorts of problems", but it was worth "looking at [the law] again".
"The first step is learn the lessons of what has worked elsewhere: tough on kerbcrawling, deal with problems of drug abuse, help prostitutes out of this industry, make sure all agencies work together," he said.
But Cari Mitchell, from the English Collective of Prostitutes, told the BBC prostitute laws "had to go".
"Three more women have been murdered, maybe more, not only the women in Ipswich, not only the women in Bradford.
"And this really is a moment when we have to take a new direction and look at what happens when you decriminalise prostitution because it's just about sex," she said.
Meanwhile, officers investigating the disappearance of York woman Claudia Lawrence have said they will be working with West Yorkshire Police to investigate any potential link with the alleged Bradford murders.
A North Yorkshire Police spokesman said: "Consultation will take place with our colleagues in West Yorkshire Police to ensure that any factors that are common to both cases are identified and investigated promptly."
Mr Griffiths is reported to be a psychology graduate undertaking postgraduate research in criminology at Bradford University.
He was arrested on Monday at his third-floor flat, which is on the edge of the city's red light district and a short distance from Bradford city centre.