The Panama Papers are not really about a central American state. They are a glimpse through a Panamanian keyhole of an orgy of tax evasion, money laundering and kleptocracy – amid the legitimate financial planning – hosted by the world’s tax havens. Seven years after world leaders came together at a post-financial crisis G20 summit in London and committed to end tax haven abuse, it is clear from these papers that no such end is in sight.

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The good intentions have translated into a blizzard of international agreements on sharing information, amnesties through which tax evaders can come clean, and prosecution drives of variable quality to nail the cheats. All are demonstrably inadequate. Information will not, and cannot, be exchanged to any meaningful extent by countries and territories whose “offer” is that they don’t ask for it or will turn a blind eye to being deceived.

Amnesties teach rich tax evaders that, even if they are caught, they will get off far more lightly than somebody overclaiming a few pounds in social security benefits. Criminal pursuit of offenders, certainly in the UK, is little more than a joke. One prosecution from 1,000 tax evaders using HSBC’s Swiss accounts is the now infamously poor punchline.

Here, the Panama Papers lay bare another national disgrace: Britain’s longstanding role at the centre of the offshore web. More than half of the 200,000 secret companies set up by the Panama lawyers Mossack Fonseca were registered in the British Virgin Islands, where details of company ownership don’t have to be filed with the authorities, never mind be made public.

While this week’s leak is on an unprecedented scale, it exposes a historic as well as current failing. As the British empire faded away after the second world war and territories such as the British Virgin Islands drifted into the constitutional limbo of semi-independence, they were encouraged to develop financial services as a way of sustaining precarious economies. If this meant a few of the world’s wealthier people paid a little less tax, thought successive British governments, it was a price worth paying for not having to support the territories.

Tax havens became parasites on the world economy, most seriously sucking the life out of some of its poorer parts

Late 20th-century financial liberalisation turned this already complacent calculation into something more lethal. With fortunes sloshing freely across borders, tax havens became voracious parasites on the world economy, most seriously sucking the life out of some of its poorer parts. All the great national robbers of recent decades, such as Nigeria’s Sani Abacha, have used tax haven companies, including British Virgin Islands ones, as the getaway cars.

Despite this long trail of evidence, leading economies refuse to address the problem at its source. The UK has great leverage over its 17 overseas territories and crown dependencies, all of which depend on the mother country for security and happily trade off its legal system. At a stroke our government could shut down the British Virgin Islands corporate system, for example. But under influence from a banking system that thrives on the legal benefits of offshore centres such as the British Virgin Islands and the Cayman Islands, it takes a more relaxed view. Asked recently about whether Britain’s overseas territories should publish registers of beneficial owners of their companies, foreign office minister James Duddridge replied that these were a “direction, rather than an ultimate destination”. The Panama Papers should expose this indifference for the great scandal that it is.

Without leaks like this week’s, nothing would be publicly known about the tax haven companies now exposed. And next to nothing would be known by the authorities in the countries affected. Yet, alongside dozens of other tax havens, the British Virgin Islands can claim to be on the Organisation of Economic Cooperation and Development’s “white list” of approved jurisdictions, having met conditions imposed for exchanging information. That’s right: a major centre of international financial crime, home to the shell companies of Vladimir Putin’s associates and any number of other money launderers and sanctions-busters, is endorsed by the rich nations’ club.

With around $1tn a year still flowing out of developing countries to tax havens, it is clear that coaxing these territories into increased transparency can achieve only marginal gains. The recent series of leaks poses a more potent threat: anybody contemplating hiding income offshore must now factor in the risk that many years later the details could make their way from an office such as Mossack Fonseca’s into the wider world. Far better, even the greediest might think, simply to pay the tax and get on with life.

But for others, especially those looting serious money, the offshore attractions will remain. There will be further added layers of secrecy: phoney foundations and fake beneficial owners with no names mentioned even in internal emails. A small proportion of scams will be exposed in the press and documentaries featuring telegenic palm trees and yachts will continue to hit our TV screens. But the tax havens will keep their place in the world.

To tackle the cancer of corruption at the heart of the global financial system, tax havens need not just to reform but to end. Companies, trusts and other structures constituted in this shadow world must be refused access to the real one, so they can no longer steal money and wash it back in. No bank accounts, no property ownership, no access to legal systems. The anti-corruption summit being hosted by David Cameron in May is an opportunity to start the international team effort that this would require. The world has been entertained by tax havens long enough.

• Richard Brooks was consulted by Panorama and the Guardian over the Panama papers