Urgent action is needed at...G20 summit in St Petersburg to fix a tax system allowing firms to "rip off" poor African nations, Oxfam has warned. Such countries were losing almost 2% of national income in tax not paid by firms, depriving them of billions of pounds, the charity said. It urged leaders to "tear down walls of secrecy" that allow tax dodging...Oxfam called on world leaders at the G20 to do more to support an automatic system for exchanging tax information to allow both rich and poor countries to access tax information. It also urged agreement on ending "phantom firms" to make sure company ownership could no longer be a secret. And it said leaders should agree to country-by-country reporting for all multinational companies to ensure transparency about where they pay taxes.