Gilles Desaulniers moved to San Francisco 40 years ago, settling in the ‘friendly, quaint and affordable’ city after running out of cash while driving from Canada down the West Coast of America.

Today he runs a grocery store filled with fresh fruit, vegan snacks and organic wines typical of this famously liberal Californian city.

But Gilles has shut one outlet and would sell up entirely if anyone wanted this one, his remaining shop.

Each day, up to 30 people stroll in and openly steal goods, costing him hundreds of dollars.

A street cleaner showed me a box filled with used syringes that he had collected, then I met two charity workers picking up needles from the pavement. How many do you find a day, I ask? ‘Between 300 and 600, depending on the weather,’ one replies. A homeless man is pictured second left using a syringe to inject drugs in the city in June 2018

He has been bitten twice recently by people in his shop and he also found a woman turning blue in the toilet after a drugs overdose, a hypodermic needle still stuck in her leg.

He showed me a metal door that is corroding due to people urinating in his doorway, then spoke of finding a man relieving himself in full view of infants playing in a child centre next door.

‘Our society is falling apart,’ says Desaulniers.

‘If people do not play by some rules, society does not function. But it feels like there is no order, there is no shame.’

He uses two apocalyptic movies to illustrate the state of his adopted city: ‘Living here feels like A Clockwork Orange and Blade Runner have both come true.’

I could grasp his despair. I had just passed dealers selling drugs beside a police car parked outside government offices, and seen their customers openly smoke fentanyl, an opioid 50 times stronger than heroin, then collapse on the street.

Yet true to form, San Francisco has just elected as district attorney a radical called Chesa Boudin, whose parents were infamous militants from a far-Left, anti-war group. They were jailed for triple murder when Chesa was a toddler, leaving him to be adopted by the founders of the organisation

All cities have their seedy sides. But this is the very centre of San Francisco, by an upmarket Westfield shopping mall thronged with people in designer clothes perusing Rolex watches, Louis Vuitton handbags and Tiffany jewellery.

The beautiful city by the bay, where Tony Bennett famously left his heart and which poses as a beacon of progressiveness, has more billionaires per capita than any other on the planet.

Not long ago, a seven-bedroom home here recently sold for $38 million (£29 million), while at the Michelin-starred Saison restaurant, the ‘kitchen menu’ starts at $298 a head and reservations require a $148 deposit.

The city authorities have a huge $12 billion budget, handing their 31,800 staff average annual pay and benefit packages of an astonishing $175,000.

Yet the tide of homeless, addicted and mentally ill people washing up here has become so severe that a global expert on slums claimed San Francisco may be more unsanitary than some of the poorest parts of Africa and Asia.

Oracle, one of the technology giants based in the nearby Silicon Valley, has switched a conference for 60,000 people to Las Vegas due to the toxic combination of ‘poor street conditions’ and costly hotels.

This followed a medical association moving its $40 million convention out of San Francisco amid safety fears because of sordid tent encampments and overt drug use. Other events are being affected.

‘Indoors, people are making deals, talking about healthcare and networking. Yet in the streets, I witnessed homeless people injecting cocaine,’ tweeted Kistein Monkhouse while attending a recent J. P. Morgan conference for 9,000 people.

As one prominent academic tells me, it seems a cruel irony that so much squalor and despair is found in the Californian base of all those billionaire technology titans seeking to reshape the world in their image.

‘San Francisco has always had hobos but we’ve never seen anything like this. It’s become a vision of some kind of strange dystopian future,’ says Joel Kotkin, a widely respected professor in urban studies.

He can reel off damning statistics to back his claim that San Francisco symbolises the Golden State’s descent into ‘high-tech feudalism’ including America’s highest poverty levels, its worst rates of property crime and its biggest gap between top and middle incomes.

But one statistic stands out: almost half of homeless people in the United States are in California, according to a recent White House study.

And San Francisco, a comparatively small city that is home to tech giants such as Twitter, Uber and Airbnb, has the highest rate of ‘unsheltered’ citizens – at ten times the national level.

All cities have their seedy sides. But this is the very centre of San Francisco, by an upmarket Westfield shopping mall thronged with people in designer clothes perusing Rolex watches, Louis Vuitton handbags and Tiffany jewellery

Downtown visitors cannot fail to witness the distressing evidence. Almost instantly after I arrived, I saw three people smoking crystal meth through glass pipes, then others with the facial scabs and sores associated with this destructive drug. One man with matted hair sat slumped in a stupor wearing just grubby underpants.

Another, clearly under the influence of heroin, had ‘nodded off’ and was static on a child’s bicycle. A third urinated on the street. A woman changed her clothes from a tatty suitcase on the pavement.

Others shuffled pathetically or rolled slowly along the street in wheelchairs. Some were clearly suffering mental distress, such as a man in his 50s begging for cash who told me he was waiting for his air force pension.

A street cleaner showed me a box filled with used syringes that he had collected, then I met two charity workers picking up needles from the pavement.

How many do you find a day, I ask?

‘Between 300 and 600, depending on the weather,’ one replies.

So if you are going to San Francisco, feel free to wear flowers in your hair but local women say avoid sandals on your feet. Dog owners complain they have to wash human faeces from the legs of their pets after a walk.

One fed-up resident showed me Hondurans handing out socks filled with wraps of drugs in front of a building being turned into an upmarket Whole Foods store.

The dealers displayed little need for concealment. ‘After a while, you become desensitised – it’s like everyone here is wearing blinkers,’ says my guide, a man in his 30s.

‘All my friends with kids have moved out of the city.’

The city and state have some of the highest tax rates in the country, but his area of SoMa West voted to back a fresh charge on firms to fund a new community group to clean up its streets. It is the 17th district to pass such a measure.

‘You have to develop a thick skin,’ says Sonya Lee, 24, supervisor in a Starbucks branch surrounded by bustling boutiques, expensive hotels and smart restaurants. ‘Every day, people come in and take stuff. It’s dreadful but we don’t know what to do.’

San Francisco, a comparatively small city that is home to tech giants such as Twitter, Uber and Airbnb, has the highest rate of ‘unsheltered’ citizens – at ten times the national level

Official data, based on one night’s count last year, claimed 8,011 homeless people in this city of 884,000 people – a rise of 17 per cent on 2017.

But a record of those receiving healthcare found numbers twice as high and rising faster.

City authorities claim their key problem is the high cost of housing combined with past failures to build enough properties. But many blame something simpler to solve: the lack of law enforcement.

‘When you tell vagrants that anything goes, it leads to the anarchy you see on these streets,’ says Heather MacDonald, a fellow at the Manhattan Institute think-tank and a conservative essayist.

She believes we are witnessing a ‘real-life experiment’ into what happens if society stops enforcing bourgeois norms out of sensitivity to vulnerable people.

MacDonald argues that the city authorities are culpable, fuelling drug addiction by doling out 4.5 million needles a year when there is nothing compassionate about giving addicts and mentally ill people the freedom to ‘decompose’ on the streets.

Much of what she says is backed by Thomas Wolf, 49, who lost his job and family after becoming addicted to opioid painkillers following foot surgery, then moving on to cheaper heroin and ending up homeless in his native city.

‘It is a cycle of despair,’ he says. ‘I was heartbroken at losing my wife and kids but all I cared about was drugs. I hated being on the streets but I loved the easy access to drugs.

‘Yet there’s such denial that if you’d have asked me if I had a problem, I’d have said no.’

Wolf, who now works for the Salvation Army helping homeless people rebuild lives and has just been appointed to a specialist civic taskforce, sees untreated addiction as the root cause of the city’s problem. He says most people living on the streets are hooked on either drugs or drink.

‘If you see someone shouting at the wall, it is crystal meth, not mental illness – although meth might have destroyed their mind.’

Wolf claims that while the city distributes drug paraphernalia, he was never asked to quit or offered help. He says many users sell their monthly welfare $190 food stamps on receipt to go on a binge. And he wants to see generous welfare benefits – almost $600 a month in return for 12 hours of voluntary work – slashed.

His own time as a homeless heroin addict ended after police caught him holding six socks filled with drugs for Honduran dealers. His brother bailed him from jail on condition that he went into rehab.

He was lucky. Last year there were 234 deaths from fentanyl and heroin in the city, more than double the previous year and five times higher than in 2016.

Wolf believes that the decision by a state ballot six years ago to reclassify thefts of property below the value of $950 as misdemeanours has backfired badly, leading to a huge increase in shoplifting.

‘It is a disaster,’ he says. ‘The idea was sound – to reduce jailing that is predominantly of minorities – but the side effect was to embolden people to commit crime with impunity. Everyone knows you can go into shops and steal up to $950.’

Even shampoo, deodorant and toothpaste are now locked up in chemist shops to curb thefts.

The police declined to speak officially. But one officer sitting in his car beside blatant street-dealing said there was no point arresting people as they would simply be released, even if they were carrying drugs and cash valued at several thousand dollars.

‘I find it very frustrating and lots of my colleagues find it very frustrating,’ he says, adding that officers only intervene when there is violence. ‘We get the blame because people think we’re doing nothing. But it’s not our fault.’

Wes Tyler, manager of a family-owned hotel, told me a man high on crystal meth smashed a $5,000 window one Sunday afternoon – then repeatedly ignored court dates and probation orders despite being seen in the neighbourhood last week.

‘If City Hall does not start to take these issues more seriously, we’ll see businesses impacted,’ says Jay Cheng, spokesman for the local Chamber of Commerce.

Yet true to form, San Francisco has just elected as district attorney a radical called Chesa Boudin, whose parents were infamous militants from a far-Left, anti-war group. They were jailed for triple murder when Chesa was a toddler, leaving him to be adopted by the founders of the organisation.

The beautiful city by the bay, where Tony Bennett famously left his heart and which poses as a beacon of progressiveness, has more billionaires per capita than any other on the planet. Not long ago, a seven-bedroom home here recently sold for $38 million (£29 million), while at the Michelin-starred Saison restaurant, the ‘kitchen menu’ starts at $298 a head and reservations require a $148 deposit

The 39-year-old, who studied at Oxford University as a Rhodes scholar and later worked as a translator for Venezuela’s former leader Hugo Chavez, a Fidel Castro acolyte, campaigned on moving away from prosecuting ‘quality of life’ offences to focus on serious and corporate offences.

The San Francisco Police Officers Association spent heavily campaigning against Boudin, saying he was the choice for ‘criminals and gang members’.

But Jennifer Friedenbach, executive director of the charity Coalition on Homelessness, argues city residents should get angry over ‘systemic neglect’ that sparked this crisis rather than blaming people on the streets.

‘No one wants to live like this,’ she says. ‘We’ve tried locking people up before but that didn’t work.’

Friedenbach insists that the problems stem from a lack of affordable housing, a significant reduction of emergency shelters and the slashing of spending on treatment programmes.

She says, rightly, that issues of homelessness, mental health and addiction are often linked.

The city’s mayor, London Breed, whose younger sister died of a drug overdose and elder brother was jailed for robbery, declined to comment.

In her inaugural speech, Breed said the ‘twin troubles of homelessness and housing affordability’ were the big challenge.

She is boosting grants for shelters, treatment and street cleaning. Yet those desperate sights staining this one-time hippy nirvana are ultimately the sign of abject political failure.

Her new fiefdom is, after all, so populated by millionaires in their exclusive enclaves that it is the second richest city in the world’s richest nation.

Considering the city’s wealth, it smacks of callous and uncaring hypocrisy.

As one local resident says: ‘Are they really being progressive to that poor guy in the street with a needle in his arm who is going to die tomorrow?’