The world's finance ministers must use the G20 meeting in Sydney this weekend to crack down on tax avoidance by multinational corporations, Oxfam says.

It says national governments lose billions of dollars each year to tax loopholes and avoidance, and that money could be used to reduce developing countries' dependence on foreign aid and lift people out of poverty.

Dr Helen Szoke, Oxfam Australia's chief executive, said the international tax regime was ''broken'' and needed fixing.

"This is contributing to widening income inequality and the scandal that we see today of the 85 richest people owning the same amount of wealth as half the world's population," she said.

"Rich corporations and individuals cannot be allowed to keep squirreling their profits away in tax havens in order to dodge their tax responsibilities."

The Abbott government has made international tax reform a priority issue for its 2014 presidency of the G20 Leaders Summit in November.

The G20 Finance Ministers and Central Bank Governors meeting, being held in Sydney this weekend, is an important precursor to that event.

Dr Szoke said this weekend's meeting had "great potential" to set the scene for the G20 meeting in November.

Her group is calling on those attending the event to tackle international tax avoidance and promote tax "transparency''.

It says that multinational corporations ought to be required to publish a breakdown of their employees' assets, sales, profits and taxes in countries in which they operate.

It also says developing countries ought to be included in the taxation reform process, and the ''Base Erosion and Profit Shifting'' project, run by the Organisation for Economic Cooperation and Development, would be the place to do it.

''To make a real impact the G20 has to look at something that is manageable, and that deals with growth while making a difference in the world," Ms Szoke said.

''Here's one thing they can focus on to make a real difference.''

The Africa Progress Panel's annual report for 2013 found tax avoidance and low tax rates meant sub-Saharan Africa lost $70.5 billion a year on average between 2008 and 2010, more than twice the amount it received in aid for the period.

It found efforts to promote tax transparency in Africa were undermined by foreign investors who used offshore companies, shell companies and tax havens.

"Such practices also facilitate tax evasion and, in some countries, corruption, draining Africa of revenues that should be deployed against poverty and vulnerability,'' the report said.

"We call on the G8 and the G20 to step up to the mark, to show leadership in the development of a credible and effective multilateral response to tax evasion and avoidance.''