21/05/2013 21:15 BST | Updated 21/07/2013 06:12 BST

The Truth About British Treasure Islands

Under the banner of our G8 Presidency, David Cameron has put himself at the centre of the debate on tax dodging. But today, Oxfam has revealed the uncomfortable truth that the UK is already at the centre - and responsible for much of - the global tax dodging scandal.

The shady and immoral global tax system is allowing a whopping £12trillion in wealth to be stashed in tax havens. Yes that's trillion. More importantly, these assets are sitting offshore and off the tax man's radar. If governments could get at it to tax it fairly, it could raise an extra £100billion, which is enough to make a serious dent in solving world poverty. It could help the one in eight people going to bed hungry tonight, and it could help to create jobs for people on the breadline here in Britain. In fact, it's enough money to end extreme poverty twice over.

But what's worse is that this is happening right under the government's noses. Our research shows that one third of the wealth ushered into tax havens is sitting in British Overseas Territories and Crown Dependencies. So the UK is responsible for one third of the lost tax revenue, and the lost opportunities that go with it. This puts Britain indisputably at the heart of a global tax system that is a colossal betrayal of people here and in the poorest countries who are struggling to get by. And it makes us the G8 member with the most to prove in the next 4 short weeks.

It's painfully obvious that when it comes to tax, that getting companies and individuals to 'play by the rules' is far from being good enough. Because you could drive a tank (or an army of accountants in a luxury yacht) through the loopholes in the rules as they stand today.

As part of the IF campaign, Oxfam is calling for some obvious and urgent changes to the global tax regime. We want to know who the ultimate owners of assets held offshore are, so that nobody can hide behind phantom firms or disassociate themselves from their own riches to avoid paying their fair share. And we want tax havens to be mandated to share information with poor countries, and to face penalties if they don't.

It's no wonder the government is starting to feel the pressure. This week David Cameron has written to UK-linked tax havens, saying the G8 will 'knock down the wall of secrecy', but without serious action ahead of the G8 Summit - now in less than a month's time - there is a real risk that other G8 nations will be asking difficult questions. And we should be doing the same, because in the toughest times we have faced for years, we need more than just talk.

From the UK we'd like something very specific. Will David Cameron manage to take advantage of this moment in the spotlight to get UK tax havens fully signed up the existing Multilateral Convention before he heads to his G8 Summit? That's what would start to sort the wheat from the chaff.