Independent MP Rob Oakeshott has sought changes in Australia's general sales tax (GST) ahead of the two-day tax forum which begins Tuesday.

Oakeshott, who sought a 10-year roadmap for tax reform, made the changes a condition for him to help Labor form a minority government.

About 200 delegates from government, business and industry have arrived at the Parliament House for the forum. Treasurer Wayne Swan, who hosts the event, said new ideas are welcome, but he definitely placed his foot down on changes to the GST.

"When it comes to the GST we've said for a long time we are opposed to increasing or widening the base.... It punishes low and middle income earners," The Australian quoted Mr Swan.

"We don't see it as a panacea - we see it as unfair - and we don't see it as the most efficient way to organise our tax system," he added.

Besides Oakeshott, the Greens also pushed for widening the GST base and increasing the rate from the present 10 per cent.

Prime Minister Julia Gillard said she is open to new ideas, but said proposals must pass the test of financial prudence.

"Clever ideas about spending money have to be matched with clever ideas about where that money is coming from, and that is a challenge for this forum over the next two days," The Australia quoted Ms Gillard.

She shared Mr Swan's concern that proposed amendments must not add to the burden of the poorest Australians. The prime minister also said changes must also take into account external circumstances such as the increasing influence of Asia and the two-speed Australian economy.

"Let's not forget that tax is the money that enables us to build a better society together.... Whether it's meeting our needs for defending our nation, or whether it's ensuring that a child can get an operation in a hospital or a disadvantaged kid can get a great start in life through a great education," Ms Gillard stressed.