DO you mind walking down the street with cameras recording your movements?

I do. Growing up in Northern Ireland has left me edgy about surveillance. Certainly there are bad people out there and watching them is an effective way to protect innocent citizens.

But when surveillance turns into watching all citizens lest a few of them act in a criminal way, my civil liberties hackles rise.

Qui costodiet ipsos custodes? Who watches the watchers? Who will hold them in check?

There are an estimated 51,600 surveillance cameras on UK streets. That's just the ones controlled by local authorities. Their distribution needs to be more carefully controlled, hedged with protection for the individual. Their effect must be measured and evaluated and the findings published.

No more should be installed until this has been done.

For they don't come cheap. Scotland has spent more than £33m on CCTV in four years – and I wonder how much we've got to show for it.

You might imagine the cameras are already carefully placed in crime hot spots. Instead they seem to be scattered willy-nilly. There is no centrally agreed policy. Each local authority makes its own decision about how many to have and where to place them.

Some supporters of CCTV imagine that the police monitor the cameras. They think that help will automatically be sent if they are attacked. Not so. Most tapes are only viewed after a crime has been reported.

Some cameras are excellent. Some are badly maintained and in others the technology is so poor that the images they produce are useless. It's a lottery – an unaffordable one.

According to The Price of Privacy published today by the civil liberties group Big Brother Watch, UK councils have spent £515m on CCTV in the four years to March 2011. In Scotland, Edinburgh City Council paid out more than £6m. Glasgow didn't reveal its bill but it has 574 cameras. East Ayrshire spent £3million and East Dunbartonshire £1.4m.

So what did the money buy? How effective were the cameras at cutting crime? Nobody knows.

You might imagine that there is a crime map over which one could lay the positions of CCTV cameras. Attached would be a graph showing that as cameras arrive, crime diminishes.

But that would belong in a rational world.

Instead the scant information available tells us that CCTV cameras can have a tremendous effect on crime reduction in car parks. A drop of 50% and more has been registered in some places. This figure tends to boost the statistic for crime reduction as a whole but when it is removed the overall difference CCTV can claim is closer to 7%.

In 2008 the Metropolitan Police undertook a study to measure the cameras' effect on solving crime. They could identify less than one crime solved per 1000 cameras.

We are the most spied-upon citizenry in the developed world. We're so accustomed to it now that we barely notice the cameras on our streets, in lifts, in trains and buses, in supermarkets. Some are managed by councils and some by private companies.

Councils use CCTV as a cheap alternative to policing when it should be a used as a well-regulated support tool.

Fife and Aberdeen City have more surveillance cameras trained on their citizens than the combined cities of Manchester, Liverpool and Hull. It beggars belief.

In England, Southampton Council insists that taxi drivers have CCTV with audio in their cabs or they don't get a licence. Oxford plans to introduce a similar scheme by 2013.

The nation has been shocked and horrified by tabloid newspapers involved in phone hacking. Outrage at the invasion of privacy involved brought down The News of the World. Journalists have been arrested. So how can it be acceptable for local authorities to film and eavesdrop on anyone who happens to hire a cab?

No doubt there will be a notice in the taxi warning customers but will people notice? The back of a taxi is a sacrosanct place. The window between passenger and driver is there to allow for private conversation. How dare councillors decree that people be taped?

Big Brother Watch is the organisation whose Freedom of Information requests have brought this unregulated excess to light. It warns that public lavatories and schools could be subject to film and audio surveillance. As with the taxis, such a scandal could only be challenged in court by a judicial review instigated by a private citizen.

The situation has arisen because CCTV has crept piecemeal across the country.

In one way it is reassuring that there isn't a centralised thought police charting our every thought word and deed. We are not living in a 21st century version of The Lives of Others, the film about surveillance in communist East Germany. On the other hand we could arrive somewhere very close to that situation if we find ourselves living in a burgh with busybody councillors who have too great a relish for power – and too little accountability in this arena.

And then there is the colossal waste of public money. It makes me weep to think of the youth charities that could have flourished with some of the £515m (half a billion) spent on CCTV across the UK in just four years.

What a dent that could have made in youth crime. More importantly, think of the lives it could have transformed for the better.

Instead of buying and maintaining cameras, that money could have swelled the ranks of the police force by 4121 constables or increased street lighting. Both measures have a proven effect on crime reduction.

The UK and Scottish governments need to take this issue by the scruff of the neck before more good money follows bad. We need to know how effective CCTV is. We need a code of practice enforced by a regulator who has teeth. We need public buy-in before more citizens' money is spent.

Technology isn't the enemy. It's just a tool that becomes the enemy in ill-natured or ill-organised hands. CCTV can't be permitted to breach our rights and invade our privacy on the grounds that we might be criminals.

Britain has 20% of the world's surveillance and 1% of its population. This filming is chaotic, it's unjust, it's ineffective, it's a criminal waste of money. It's time to shout "Cut".