London  - The British government announced plans Wednesday to clamp down on prostitution involving women who are controlled by pimps or have become victims of so-called sex-slave trafficking, mainly from Eastern Europe and Asia.

Men who have sex with women trafficked or forced into prostitution would in future face prosecution as paying for sex with a woman "controlled for another's gain" would become a "strict liability offence," Home Secretary Jacqui Smith said.

This means that prosecutors would not have to prove that the men knew a prostitute was being exploited in order to charge him, she explained.

"There will be no more excuses for those who pay for sex. That is why I am determined to shift the focus on to the sex-buyer, the person responsible for creating the demand for prostitution markets which in turn creates demand for the vile trade of women being trafficked for sexual exploitation," said Smith.

The proposals, expected to come before parliament next month, were drawn up following a six-month review which examined vice laws in other European countries, including Sweden and the Netherlands.

The measures are aimed primarily at clamping down on the growing "sex trade" involving women being smuggled into Britain from Eastern European countries.

"What I disapprove of is women being exploited in this country, coerced, trafficked into the country, effectively treated as slaves," Smith said.

The government had considered banning paying for sex altogether, said Smith, but realized that there was no public support for such a drastic move.

Under the revised laws, buying or selling sex would remain legal, while "soliciting and pimping" would become a criminal offence. Kerb crawlers can in future be prosecuted for a first offence, rather than for "persistent activity."

"My proposal is that men should think twice about paying for sex. Trafficked women don't have a choice; men do," she said.

Smith said up to 70 per cent of the 80,000 prostitutes in Britain were controlled by pimps or had been trafficked into the country and the government was working closely with the police on plans to enforce the new laws.

While groups supporting trafficked women Wednesday welcomed the proposals to "protect vulnerable women," the English Collective of Prostitutes, which represents prostitutes, warned that the new laws could have a "damaging impact on those who sell sex by their own choice."

"Bitter experience tells us that any law against consenting sex forces prostitution further underground and makes women more vulnerable to violence," spokeswoman Cari Mitchell said.