NEW DELHI: Sitting on a cold concrete slab, Sunita Devi reapplies her red lipstick as she prepares for customers at a dingy brothel along the Indian capital's infamous Garstin Bastion road.

"We don't go to men, they come to us. We want to earn a living with dignity just as in any other profession," Devi, dressed in a traditional cream and green 'shalwar-kameez', told AFP, in the bustling red light district.

Like millions of other sex workers, Devi, 35, is anxiously waiting for the country's highest court to hand down a ruling which they hope will finally clarify the age-old profession's legal status.

Soliciting is illegal in India along with running a brothel and pimping, but the law, an archaic throw back to British colonial times, is vague on prostitution itself.

Sex workers are hoping the Supreme Court's ruling will force the government to decriminalise the industry.

They say they are tired of being randomly targeted by police and sent to correction homes where they say conditions are worse than jails.

Some 2,800 women and 4,800 men were arrested in 2013, the latest government figures show but with a conviction rate less than 35 per cent, cases continue to languish in courts for years.

"Don't look at us as if we are criminals and please don't arrest our clients," said Devi, who was sold by the boyfriend she eloped with for 50,000 rupees (around $800) to a man who in turn struck a deal with a brothel pimp.

Devi opted to stay on at the brothel, where clients buy a token and select a woman of their choice, once she realised she could earn "a good 500 rupees ($8) a day or more" without having to "work too hard".

On average, she sees two men a night, up to five in busier times, in windowless cubicles with single beds.

Forced underground

India has nearly three million sex workers, according to Havocscope, which focuses on black market industries worldwide.

Activists argue many are selling sex by choice, neither having been trafficked nor held against their will, and should have the same rights as other workers.

"The law is very ambiguous. Who is exploiting whom? The woman who gets paid or the one seeking pleasure?" asked Tripti Tandon of the Lawyers Collective advocacy group.

"The law assumes that all sex workers are victims and fails to recognise their right to a livelihood. The sex workers don't consider themselves as victims so why impose it (the law) on them?"

Public health workers want decriminalisation, saying women and clients are forced underground for fear of arrest, making it difficult to limit the spread of HIV and other diseases.

But anti-trafficking campaigners argue any kind of legitimacy would fuel the industry, leading to a jump in smuggling of mainly poor and uneducated women from rural areas as well as children into brothels, a major problem in India.

Just over 14 million adults and children are trapped in modern slavery in India, the most in any country in the world, according to the Walk Free Foundation's 2014 Global Slavery Index.

Acting on a public interest petition four years ago, the Supreme Court formed a panel to investigate the industry and look at amendments to the law.

It also asked the state governments to conduct an ongoing survey to determine how many sex workers, given a choice, wanted to be rehabilitated and retrained in other professions and how many wanted to stay put.

'Income is good'

Dressed in garish saris and skirts, some waiting for customers along Delhi's seedy GB Road said they were reluctant to leave the job, because the money was better than other low-paid labour as domestic servants or seamstresses.

"We have a lot of freedom here and the income is good," said Kusum, who earns around 20,000 rupees ($317) a month for her husband and three children living in a village in neighbouring Uttar Pradesh state.

"I can afford a better life for my children back home with the money that I make here. I think my job is less strenuous than many others," said the 36-year-old, who entered the trade on the advice of a friend, also a prostitute.

While she works, her husband cares for the children who think she is a nurse in Delhi.

Although most sex workers want decriminalisation, they are wary of suggestions to licence sex work as in other countries.

Under such a scheme, they would be issued identity cards stating their stigmatised profession and also forced to pay taxes.

"Licensing might work in the West but here in India where sex work is looked down upon and prostitutes ostracised, it is a long shot," said Amit Kumar, national coordinator of the All India Network of Sex Workers.

The National Commission of Women, a federal body, briefly backed legalising the trade last year, only to reverse its stance after a fierce backlash in socially conservative India.

But Kumar said the courts and government groups needed to understand that keeping sex work in the shadows was a waste of time.

"Our politicians and courts have been fence sitting for too long. Sex work is the oldest profession and it's not going to end ever."