As Australia trumpets the need for a global crackdown on corporate tax avoidance at this weekend's G20 summit, the Tax Office is grappling with the loss of thousands of its staff, many in key areas.

More than 2200 people have now left the agency under budget cuts required by the government by 2017, including more than 500 members of its audit team. A further 2500 will be required to leave over the next three years to meet a target of 4700.

Thousands of ATO staff face cuts at a time when tax authorities around the world are poring over one of the biggest tax leaks in history. Credit:Andrew Quilty

Recent cuts were made as part of the government's efforts to "reduce the footprint" of the public service.

The audit team is responsible for enforcing the tax compliance of individuals and multinational companies - one of the core roles of the ATO and in the spotlight following high-profile allegations of profit shifting by multinational firms.