LAST week I spent a few days in San Francisco. A liberal, progressive city of diversity, culture and very real charm.

Its people are warm and welcoming to visitors. It is a city with a radical tradition, most famously a place which led the world in progressing LGBT rights and where the Chinese and Latino communities successfully resisted attempts to drive them to the city’s periphery.

Today it is a Democrat stronghold with a significant green movement.

But like many tourist hotspots across the world — Barcelona, London and Edinburgh to name but a few — San Francisco sees itself in the midst of a property price boom and crisis, buoyed by record visitor numbers and high jobs growth across California.

Whether you see what is going on as a boom or a crisis depends upon your circumstances.

If you are a property developer buying up apartments to service the year-round short-term letting tourist market, or the new techies taking up high-paid jobs with the global giants, then you are a beneficiary of the new San Fransisco gold rush.

Rents for a one-bedroom apartment sit at around $3,700 (£3,000) a month — about what I pay in mortgage for a year for my home.

With 29,000 jobs being created in California every month, many in the IT sector, property inflation is sky high.

Public-sector workers such as teachers and firefighters, low-paid service sector workers and migrants unaware of their rights have been forced out of their homes by soaring costs and exploitative landlordism.

Large swathes of people cannot afford to remain in the communities they grew up in. For those who are at the sharp end individuals and whole families are being left homeless.

Add to this military veterans, previously institutionalised mental health patients and those with no access to healthcare, and we see a beautiful, liberal and progressive city unable or maybe unwilling to support its working class and its poorest, most vulnerable people.

As I walked through one of the main shopping areas of the city, I saw the all too evident consequences of the gross inequality of this city.

A young, bare-footed and bare-chested filthy man in rags, wandered the streets screaming and punching himself in the head before delving into bins to recover discarded McDonald’s cups and soda cans to drink the dregs.

Meanwhile, 30 yards up the road the famous jewellery store, Tiffany’s was selling silver dog bowls for $2,500 (£2,030).

The man I saw was far from alone: there are an estimated 10,000 homeless people on the streets of the city, many congregating in the Tenderloin district.

Speaking to a young musician and activist in the city, he explained to me that the growth in the number of mentally ill street dwellers began during the Reagan era.

His presidency drove an ultra-free-market, small-state agenda — public spending was slashed, the private sector ruled and cash was king.

The mass closures of large mental institutions was supposed to be followed by a programme of supported care in the community, but tax giveaways and spending cuts put paid to that.

With no through care or medical insurance, the mentally ill have been abandoned, living out their crises in a very public and tragic way.

In more recent years neighbouring states like Nevada have actively encouraged some of their most needy citizens to move out of their home state to San Francisco by literally providing them with a one-way bus ticket — out of site out of mind — reducing the drain on their state budget.

Over the decades as pressure grew for more housing, restrictive planning policies curtailed new housebuilding on the scale required, and herein lies the dilemma.

Policy-makers, under pressure from the environmental lobby and others, prevented new housing projects being built, yet many of the same voices demand that the housing and mental health crises be addressed.

This contradictory position means the city cannot meet the housing needs of all its citizens. Market forces and political timidity has resulted in social cleansing with the low-paid and working class being driven from their communities.

It is of course understandable that people want to preserve their cities and towns from unrestricted urban sprawl or identikit housing that destroys their character, but if we do nothing then the alternative may see Edinburgh follow San Francisco.

By restricting housing development and failing to address the dominance of short-term letting, the laws of supply and demand play out, with appalling consequences.

As housing becomes ever more scarce and prices are soar, those whose salaries can’t keep up are driven out. The result is brutal and tragic.

Back home during the passage of the recent Planning Bill in the Scottish Parliament we had the chance to take steps to address the explosion in the short-term letting market — but an alliance of Nationalists and Tories defeated this progressive move. This was an appalling capitulation to powerful big business interests.

If we continue to see cuts to council budgets and a failure to build new council and housing association housing in the city centre, then the social cleansing of Edinburgh is inevitable.

Every morning I walk from Haymarket to the Parliament. In the last nine years I have seen the number of people living on the streets increase dramatically. These are our fellow citizens who we have a collective duty to and responsibility for.

As I write this I am reading about the HIV outbreak in Glasgow (the longest in Europe).

I see in my own region the mental health crisis, with over 900,000 anti-depressants dispensed to a population of 800,000 in the last 18 months.

And I see drug and alcohol users desperate for help being forced to wait about a year to get a consultation with a psychologist. I hope I am wrong but in San Fransisco’s housing and mental health crisis I may have just seen the future.

Our political leaders cannot allow this to happen.

Neil Findlay is Labour MSP for Lothian — follow him on Twitter @NeilFindlay_MSP.