On July 4, 2000 John Howard renewed his pledge that the GST will not rise above 10% during doorstep interview at 10 Downing Street, London. Courtesy: Seven News.

CLOSING tax loopholes that help the rich get richer must be part of any future tax reform, Labor leader Bill Shorten will tell a Melbourne conference today.

He’ll also reaffirm his strong opposition to raising or broadening the base of the GST, calling for a “bigger conversation” about tax.

Mr Shorten will tell the Economic and Social Outlook Conference tax loopholes are unfair because they are two and half times more likely to be used by the wealthy.

He will claim “gaming our system” doesn’t require any illegal behaviour, just a “well-paid tax agent”.

Prime Minister Malcolm Turnbull opened the conference on Thursday by telling attendees any changes to the tax system must pass a fairness test.

But Mr Shorten will today suggest GST changes would inflict “the heaviest punishment on those least able to afford it”.

He’ll also speak about the need for superannuation reform.

Liberal Senator Ian Macdonald spoke out against raising the GST this week, telling a radio station the Howard Government “swore in blood” it wouldn’t exceed 10 per cent.

Video footage from 2000 shows then-Prime Minister John Howard asserting that the GST would “absolutely” stay at 10 per cent.

“No government that I’ve got anything to do with will ever do anything about increasing that rate and I don’t believe that a coalition government led by somebody else, sometime into the future will do anything about it either,” he said.