SA-BEST leader Nick Xenophon has dismissed polling that he may not win his own seat at this weekend’s South Australian election.

A Galaxy poll commissioned by The Advertiser for the seat of Hartley, incumbent Liberal MP Vincent Tarzia pulled the highest primary vote at 38 per cent, ahead of Mr Xenophon on 30 per cent and Labor candidate and former minister Grace Portolesi on 22 per cent.

The poll, which surveyed 590 voters last Saturday, showed Mr Tarzia also leads Mr Xenophon 51 per cent to 49 per cent in the two-party preferred vote.

Mr Xenophon told Sky News he had deiberately chosen the hardest seat to win.

“This is like climbing Mount Everest without oxygen on crutches,” he told reporters on Sky News.

Meanwhile, the Liberal Party is rolling out a campaign claiming Labor “has a secret plan” to increase the GST to 15 per cent.

Opposition spokesperson Rob Lucas denied the campaign was a scare tactic, pointing to a push from Premier Jay Weatherill in 2015 to increase the tax to cover rising health costs.

Mr Weatherill’s push failed, because any change to GST arrangements need the consent of federal and state governments.

Mr Lucas said Labor would have to find more revenue, to pay for its more than $2 billion worth of election promises.

-AAP, ABC