Church groups are demanding that Gordon Brown closes legal loopholes used by the super-rich to avoid tax.
This weekend, Christian Aid, Cafod, Church Action on Poverty and the Church Council for Monetary Justice all made statements, quoted in the Observer newspaper, urging the Chancellor to tackle what they see as a new frontier in an anti-poverty agenda.
With concern mounting over the widening gap between rich and poor in Britain, loopholes have led to Britain being labelled a tax haven by the International Monetary Fund.
The Treasury recently revealed that, since 2002, only three officials have been working on its review of non-dom status but have so far come up with no conclusions.
It is reportedly blocking requests to establish how many people claim non-dom status and how much tax has gone through the loophole.
Non-dom status allows the wealthy to legally escape paying tax on earnings abroad.
Andrew Pendleton, a senior campaigner at Christian Aid, said: "This is an economic issue. But it's a moral one too. Is using perfectly legal methods of minimising tax right? The answer is no."
"As finance ministers fret over reaching aid commitments they made at Gleneagles, they should also be focusing on how they have allowed millions of dollars to pour through tax havens, draining developing countries of far more resources than are going in as aid," said George Gelber, head of public policy at Catholic aid agency Cafod.
Niall Cooper, national coordinator of ecumenical Christian charity Church Action on Poverty, said: "Most of the population does not have the opportunity to avoid tax. Tax isn't a voluntary activity."
There is an estimated $11.5 trillion held in tax havens by high net worth individuals. The annual income of over $800bn far exceeds aid budgets of $100bn.