More than 700 people are killed by heroin in Britain every year: most die from overdoses, accidental and deliberate, but many victims are addicts whose bodies simply succumb to years of abuse and neglect.

Then there is the collateral damage: the victims of the countless muggings, thefts and burglaries committed in pursuit of the next fix; the squalid lives of the young women driven by the craving for drugs to sell sex cheaply on the streets and make themselves vulnerable to beatings, rape and - in the case of the five heroin-addicted victims of the Suffolk Strangler - murder.

Terrorism, by contrast, killed no one in Britain last year, nor the year before and has not claimed a life since July 7, 2005, when Mohammad Sidique Khan and his cohort murdered 52 London transport passengers. Since then there have been plots and attempted attacks - some sophisticated and ambitious, others crude and inept - but al-Qaeda has been thwarted.

Yet it is terrorism that Gordon Brown says we must fear above all else. There are, he and his ministers and security officials keep telling us, 30 active plots against Britain - although keen observers might note that the number never seems to change no matter how many conspiracies are foiled.

Fanatics in faraway caves cooking up ever more barbaric plans to bomb their way to a global Islamist dictatorship are “the most serious and urgent” danger to the citizens of the UK. Mr Brown is so concerned that he is preparing to stake the remnants of his political reputation on securing ever more draconian legislation to fight terror. The intelligence services and Scotland Yard's Counter-terrorism Command are swelling in size, absorbing the great bulk of the £2.5 billion security budget, which will rise to £3.5 billion by 2011.

Close behind the terrorism, the National Security Strategy lists the world's “great insecurities” as war, poverty, disease and climate change. Then, almost as an afterthought and barely warranting a mention, there is organised crime - the activity that delivers 30 tonnes of heroin on to British streets every year and wreaks far more death and destruction than 30 amorphous terror plots.

The heroin trade is the most easily illustrated example of how organised crime operates today. The business of producing, smuggling and selling heroin employs thousands of people around the world: poppy farmers in Helmand, Afghan warlords, corrupt politicans, police and border guards across many countries, Iranian truck drivers, Turkish drug barons, Dutch wholesalers, British distributors and street-corner dealers.

But crime bosses do not limit their activity to drugs. They are businessmen, constantly diversifying into new markets in pursuit of profit. They have trafficked thousands of women and girls into Britain and coerced them into the sex industry; the smuggling of illegal economic migrants occurs on an even larger, and more profitable, scale; a booming trade goes on in contraband cigarettes and counterfeit designer goods; £15 billion of criminal profits is laundered through the British economy each year; and systematic fraud accounts for some £20 billion annually. This extensive shadow economy is underpinned by the trade in illegal firearms - an essential enforcement tool for any serious criminal.

Behind these statistics lurks the corruption of our way of life, as so many Britons have become eager consumers of the produce of organised crime. Does anyone buying a pirated DVD from a young Chinese woman in a pub give a thought to the likelihood that she has been enslaved by a “snakehead” gang to pay off the heavily inflated price of her illegal passage to Britain or risk violent retribution against relatives in Fujian province?

It took 9/11 to force Britain to take the Islamist terrorist threat seriously. Since then the counter-terrorism agencies have turned Britain into a hostile environment for terrorists. Organised crime, however, doesn't do spectaculars. The men behind it are interested in profits, not propaganda and, as a result, their reach into our society is much more insidious and unchecked than that of terrorism.

The mismatch between the resources devoted to fighting organised crime compared with those directed towards counter-terrorism is unnerving. Government says that there are millions of pounds in police budgets that should be devoted to dealing with organised crime. In truth, only a handful of British police forces know how to tackle it. The ridiculous Victorian patchwork of shire constabularies means that most are too small to tackle serious criminality that doesn't recognise country, never mind county, borders.

The Serious Organised Crime Agency (Soca) was launched two years ago as Britain's equivalent of the FBI, with the remit of taking on the Mr Bigs of international crime. But ministers have trimmed Soca's budget this year. Far from expanding to counter the ever-growing threat, the agency is shrinking and there is smouldering unhappiness in the ranks. Soca's budget for taking the fight to the cartels and syndicates is £400 million - exactly the same amount that the Government intends to spend overseas in countries such as Pakistan on workshops and seminars to counter al-Qaeda's ideology.

Meanwhile, the demands on Soca have increased as MI5 and MI6, realising the big money (and their future) is in terror, have all but abandoned the fight against international crime.

Terrorism is a high-visibility threat and rightly commands a well-resourced and highly visible response. Serious organised crime prefers to operate in the shadows - beatings behind the locked doors of brothels, drug deals done in dank stairwells on sink estates. But out of sight should not mean out of mind.

Sean O'Neill is crime and security editor at The Times

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