Joel Edwards, from Micah Challenge, made the comments after a series of events highlighting the issue of tax avoidance were carried about by a campaign group he is a part of.
The EXPOSED campaign group held a roundtable event which included business leaders, academics, church pastors, lawyers and tax experts. All of them called on the G20 to stop tax avoidance by companies.
Previously, they protested by setting up a mock tax haven in Brisbane's central business district.
At this demonstration, an Australian politician was given an open letter signed by 95 church leaders from across the world, representing approximately one billion Christians, calling for the G20 to stop corporate tax avoidance.
EXPOSED says developing countries lose $160bn (£102bn) a year because of companies avoiding tax.
Joel Edwards told Premier's News Hour: "The G20 have woken up to the fact that everybody benefits from having tax dodging dealt with quite severely. We're seeing very clear, significant signs that that's about to happen.
"All the indications are that the G20 nations and certainly the Australian government who's hosting the G20, are very very serious about closing the loophole on tax-dodging which caused this dishonesty from multinationals.
"Governments have come to the conclusion that it's just good business sense to close these gaps, not only because it damages people in very poor nations but actually it also leads to a lack of revenue for wealthy nations."
The G20 summit is an annual conference of leaders from the world's twenty richest countries, which meets around the world. It's gathering in Brisbane, Australia, this weekend.
