In the street of a city which, more than most, lays claim to the boast, Scotland with Style, a man is urinating against the railings of a stranger's tended garden.

On the pavement, discarded bread rolls ooze ketchup slime. Chips from a takeaway carton are strewn over steps leading to an innocent neighbour's front door, and two empty beer cans have been stuffed into the hedge. It is 5am, and from a third-floor apartment window the sleepless witness watches night pale into another disheartening day.

This is but one desecrated corner of a metropolis proud to call itself the third busiest visitor destination in Britain. To that distinction we can add another: Glasgow is well on the path to being the most slatternly city in the UK, far ahead of its cultural rivals in Manchester, Liverpool, Newcastle and Leeds. So, unless the city's compulsive litter vandals cease to scatter their squalor with gusto and no single thought for anyone, Glasgow's advancement in so many other areas will not be the lasting impression held by guests from elsewhere attending the Commonwealth Games.

There are 20 months to go to 2014's opening ceremony, not long to shift the mindset of a wilful litterarti. But in preparation for the Games – and the Gleneagles Ryder Cup – the grassroots movement Zero Waste Scotland has just gained £300,000 to add to the £1.8 million already received from the Government "to spearhead new ways of cleaning up litter". Also towards this goal the environmental charity, Keep Scotland Beautiful plans next year to recruit one million tireless folk prepared, in all weathers, to black-bag the rubbish thrown down by yobs.

This will be the biggest, nationwide sprucing operation in Scotland. But will it work? Some years ago in an interview with Charles Gordon, boss of Glasgow City Council at the time, our conversation turned to litter, a subject on which Mr Gordon was eloquently angry and candid. "It's not the council that's throwing down litter," he said. "It's Glaswegians. We're a dirty city." Staff had shown him a video of Sauchiehall Street at 8am when it was pristine after the street cleaners had done their round. Thirty minutes later, the video revealed it was filthy again, the territory of feral pigeons. "It's heartbreaking" Mr Gordon continued. "We've got to change this attitude which thinks it's all right to chuck rubbish in the streets because someone else is employed to pick it up." In a concluding blast, he declared: "This isn't a class thing. It's an all-class thing."

He was right on that score. Walk behind rush-hour commuters and you see people in business suits with briefcases, throwing debris on the ground. Tackle them about it – "Excuse me, but I think you've dropped something" – and you're liable for a mouthful or worse. Even Alice Arnold, the diminutive Radio 4 newsreader, realises she was lucky when last May she lobbed back the empty plastic bottle thrown from a car window, and in return received only mute astonishment from the vehicle's occupants. But ever since that small, heroic deed, she has heard of people being threatened with violence for doing something similar.

And that's another thing about litter: it often signifies an underlying rage in the offender so close to the surface it can be triggered by the mildest rebuke. For the American satirist David Sedaris, litter represents a brand of anger which says to the rest of us: "To hell with you." But who are the rest of us? In a recent survey Keep Scotland Beautiful discovered more than half the Scots questioned, admitted to dropping litter, and half of them thought so little of it, they did so time and time again.

Here, opposite Glasgow's showpiece Botanic Gardens, we see the wilful detritus which greets citizens, tourists and long-suffering street sweepers every morning. When, in a spasm of public- spiritedness, residents set to and clear some of the grunge, those passing by presume we're the recipients of court-ordered community punishments. But think of it this way: keep on like this with our fouling habits and the rats will win.