On the ABC's 7.30 this week, former treasurer Peter Costello said major tax reform in Australia had become almost impossibly hard.

"If you're going to have a discussion about tax reform, it's preferable to start when you've got a bit of padding amongst public opinion because this is hard," he said.

Treasurer Joe Hockey says tax reform would be difficult to sell. Credit:Andrew Meares

"This is harder than balancing a budget, and I've done both, and major tax reform is off the Richter scale."

He was talking about the GST, but his comments can be applied more broadly.