LONDON - The government could decriminalise some brothels under new plans which mark the biggest shake-up of prostitution laws in 50 years.

New penalties against pimps and those caught paying for sex are being considered, alongside the option of introducing managed zones where prostitutes could work under police surveillance, to prevent attacks.

The plans, published in a Home Office consultation paper on Friday, are designed to break the links between prostitution and organised crime, trafficking and drug abuse -- the government estimates 95 percent of street prostitutes are drug-users.

"The realities of prostitution, both for those involved and for the wider community, are often brutal," said Home Secretary David Blunkett in the paper.

Existing laws ban kerb-crawling, soliciting, pimping and brothel-keeping, but sex workers are more frequently prosecuted than clients.

Around 80,000 women work as prostitutes, more than half of whom are under 25, according to official estimates.

Only a fraction work on the streets but they often shun police and fail to report attacks because they fear arrest.

The International Prostitutes Collective lobby group is unconvinced about the plans. It notes that in the Netherlands, only 12 percent of women work in managed safety zones as they prefer to stay anonymous.

"Targeting clients and extending antisocial behaviour orders will make women more vulnerable and if the government is serious about protecting women it should decriminalise prostitution altogether," said a spokeswoman for the Collective.

The last major revision of prostitution laws took place in the 1950s. The world's oldest profession is legal in other European countries, including Germany, the Netherlands and Greece and not illegal in France and Italy.

"We will welcome changes in the law which make it easier to successfully prosecute those who abuse and exploit and which at the same time make it easier for prostitutes to exit from the activity," said the Association of Chief Police Officers.