We need to be careful round here because the police could turn up at any minute and Vania knows what they're capable of.

Most days, she comes to this part of Sao Paulo to sell clothes and trinkets by the side of the road, but the street is a fragile skin in Brazil and the police are a constant threat. They have no feelings, says Vania, they're not human. And as she talks, she keeps a constant, anxious watch around her.

The pitch where Vania sells her clothes is in the busy, upmarket Santa Cecilia region of Sao Paulo. Just a few streets away is an even swankier part of town known as Higiaenopolis, which literally means "clean place" and where the apartments sell for millions. All day, people stream past and while some of them glance at the goods Vania has for sale, most rush by; others give her abuse and tell her to get off the streets. The merchandise is laid out on a sheet so Vania can sweep everything up and make a run for it if the police show up. She gives me a demonstration of how quickly she can make an escape and I count: four seconds, five seconds tops.

The reason 58-year-old Vania has to live and work like this, constantly on edge, is that she has no legal right to be here.

The law says she must not sell on the street, but she has to because she has no other way to make a living. It means she's pretty much constantly stressed, although when I talk to her between customers, she laughs as much as she cries. She laughs because she's resilient, but what makes her cry is remembering how she got here. "I needed money; otherwise I would be on the street and doing nothing," she says. "And who pays my bills? I do. I have no one."

What helps Vania cope is her informal network of friends and allies. The local priest lets her hide her merchandise in the church, and she gets advice from an organisation called Gaspar Garcia, which is supported by the charity Christian Aid and works with people living and working on the street and in the slums and favelas. The street vendors also look out for each other as much as they can - friends on the edge.

The reality in Brazil is that most of those living closest to the edge are women. The country has seen massive economic expansion and its influence and profile has grown. But it remains a violent place (it has one of the highest murder rates in the world) and a profoundly unequal one - 16million of the 200 million population lives in extreme poverty.

And it is women who are disproportionately affected. The average Brazilian woman earns 30 per cent less than the average man and according to some estimates, as many as one in three women in Brazil have experienced violence, partly because so many women, like Vania, are forced to live and work in vulnerable situations. But the violence also happens because there is widespread machismo in Brazil, and acceptance of it - among men, among women, and even sometimes among those you would expect to know better such as community and church leaders.

The situation for women has been made even worse by Brazil's economic expansion, with events such as the World Cup and next year's Olympics increasing the market for prostitution. Nearly half a million visitors are expected in Rio for the Olympics, from all over the world including the UK, and more than one of the women I speak to mentions the attitudes that some of those visitors take with them and the way Brazil is portrayed abroad (usually through pictures of Carnival women in small bikinis). The women tell me that some male visitors see Brazilian women as a natural resource - all you have to do is grab. Prostitution is also common around big building projects, with some companies openly running brothels and even handing out vouchers to staff.

There is a campaign for change, organised by groups such as Gaspar Garcia, to make things better by helping women on the edge - women such as Vania. But it's a hard battle, partly because of public attitudes but also because, as Vania has discovered, there is a lack of sympathy from the police. Above one of the stalls in the centre of Sao Paulo, there is a piece of graffiti, painted in vivid three-foot high letters, that reads "FODA SE POLICIA". You don't need to speak Portuguese to know what the four-letter word means.

And who can blame people for distrusting and disliking the police? The "pacification" programme aimed at clamping down on the drug gangs in the favelas hasn't helped, but look at what's happened in the last few days alone. In Rio, where the Olympics will be held, riot police forced people from land intended for a new hotel, adding to the suspicion that big business comes first. And in the city of Curitiba, 150 people were recently injured when police fired rubber bullets and tear gas at a group of protesting teachers. It all means that progress on helping the vulnerable in Brazil is difficult.

I see exactly how difficult it is when I visit the main police station in Ariquemes, a city in the north-west of Brazil with a reputation for violence. When I arrive in the middle of the morning, there have already been two murders; the police have also arrested a man who was chasing his wife down the street with a knife. One of the officers, 49-year-old Danubio Gurgel, holds up the knife to show me and at the back of the station I can see the dark cell holding the arrested man; all I can see of him is his fingers curled round the bars.

Officer Gurgel says he often sees cases such as these and blames the testosterone-filled Brazilian culture. "Problems with alcohol and jealously are the reason for violence," he says, "and machismo, which is still predominant in society. Men still see women as their personal property and it happens in all social classes.

"Brazil is also a very violent country and violence against women is part of that and our legal system is not being applied as it should be. We have good laws, but they are not being applied."

I ask him about the attitudes of his own officers - could they be better? "We are doing our best," he says. But that's not what I hear when I talk to the campaigners who are trying to improve the position of women. They tell me that women who complain to the police are often not believed and that many officers think women should stay quiet - and stay at home.

A few streets away from the station, a 29-year-old woman called Elineide Oliveira gives me her take on the situation. Elineide is a minister with the Parish of the Holy Trinity Church in Ariquemes but she also runs the only women's safe house in the region and has seen for herself how women are dealt with by the police.

"The kind of attention that women get at the police station is not very nice and is not what it should be," she says. "It starts in the women's house when the police officers arrive and they ask: why have you been beaten? Or what have you been doing to suffer this violence? And this kind of question continues in the police station."

We talk about what officer Gurgel said at the station, that machismo is to blame and Elineide smiles ruefully. Machismo is part of the problem, she says, but often the machismo and sexism comes from the police. "They have no kind of training to deal with women," she says. "Especially abused women - they don't know how to handle it." Trust in authority is so low that not even the police know the address of the safe house.

Over cake and coffee in the house, Elineide tells me the shocking reason why she feels so committed to this place. Fifteen years ago, her sister Elione was stabbed seven times by her husband and was lucky to survive. She introduces us to 35-year-old Elione, who says she spent eight days in hospital but felt she had to leave before she was properly recovered to protect her children from her husband. The most shocking fact? Elione's husband was never prosecuted and is still free.

Both women say part of the problem in trying to secure convictions is that corruption among the police is common, which means that laws protecting vulnerable women at home or on the street (and they do exist) are often not enforced. If a man is accused of beating his wife, he can sometimes talk himself out of trouble and even if he doesn't, the judicial process is slow and unsympathetic. Out on the streets as well, women like Vania also have to face police corruption.

Under the shade of a tree outside the church, as she sorts and re-sorts the clothes she has for sale, Vania tells me about police corruption she has faced. "I've had many bad experiences," she says. "Two weeks ago, they took all my merchandise as if I was a criminal. Working honestly is not valued here."

The police are supposed to record the confiscated merchandise, she says, so that vendors can retrieve it, but Vania says the officers often keep it for themselves, which puts more pressure on an already precarious existence. Vania has been working on the streets like this for 15 years and lives in a one-room flat. I ask her if there is any alternative to working on the street and she shakes her head and repeats the same word several times. Nada. Nada. Nada.

Other street vendors have faced even worse situations. In the Lapa region of Sao Paulo, I talk to another trader called Kelly. The 42 year old runs a stall on a busy crossroads, helped by her three children. Leaning against a wall out of the sun, she talks about her day-to-day life and the kind of violence she has seen meted out by the police.

Just a few months ago, for example, a street vendor in this part of the city called Carlos Braga was shot dead by a policeman in broad daylight; it would appear that the officer has never been disciplined. On another occasion, says Kelly, the police were ordered in to clear the traders with tear gas and rubber bullets. "I was there," she says. "There were a lot of us and the police were shooting. They are very violent and a lot of people were injured."

Kelly, who has worked as a street vendor here for 25 years, says this kind of violence from the police is common. "The authorities should look at the street sellers like real people, like citizens," she says. "I'm just somebody who wants to work."

Kelly is hopeful of some change though. For many of the traders here, she is a mother hen; they come to her for advice and, with the help of the Gaspar Garcia organisation, they are working together to change their fortunes. Six years ago, the city's mayor started to revoke the traders' work permits in an effort to "clean up the street". The same thing is happening all over Brazil, but together with around 200 vendors, Kelly is part of a class legal action to win their permits back. Her arms crossed in front of her defiantly, she says she is determined to win.

But even if she does, it will be a small victory in the battle to change the fortunes of women. Just along from Kelly's stall, 68-year-old Edineusa Des Santes sells children's clothes with all the familiar logos and pictures (Peppa Pig and Frozen have reached here too) and, as we shelter from the rain under a tarpaulin, she tells me the law doesn't benefit people like her: women, the poor, the vulnerable.

And she's right. While I'm talking to Edineusa, a local official turns up and starts throwing his weight around. What are we doing here? Why are we taking pictures? Do we know that he is in charge? We could get into trouble if we don't clear off. And so on.

It's intimidating, but nothing to what women out on the street - and in their homes - face every day. If there is any hope of change, it lies in a law which the Brazilian President Dilma Rousseff passed a couple of days before my visit to the market. It changes the country's penal code to make the killing of women a specific offence and lays down a range of tougher penalties, and some of the women I speak to are hopeful that it is a sign of change.

But there have to be severe doubts about whether it will be properly enforced. Every law needs allies and that means the police, the judiciary but most importantly public opinion. And so much of what I've seen and heard here - Vania's anxious life by the side of the road, the officer holding up a knife in the police station, Elione's story of being stabbed seven times and nothing being done, and the shocking reality of Carlos the street vendor being shot dead in broad daylight - leaves only one grim conclusion: change will be a long time coming.

 

Christian Aid works with some of the poorest people in almost 50 countries, through local partner organisations, to end poverty.
This Christian Aid Week (10-16 May) thousands of volunteers across the UK will take part in Britain's longest running door-to-door fundraising week to raise money for its vital work with communities like those in Brazil featured here.
You can help to change the lives of women in places like Brazil this Christian Aid Week by donating online at www.caweek.org,  calling 08080 006 006, or texting 'WEEK' to 70040 to give £5.