Mr Abbott ruled out making unilateral changes to the GST at a press conference in South Australia yesterday.

"Absolutely nothing can happen to the GST unless all the states agree," Mr Abbott said.

"I want to say very clearly to the people of Australia, particularly the people of South Australia and Tasmania, there will be no change whatsoever to the GST unless all the states agree."

Those words were not enough to convince Premier Lara Giddings that her GST revenue was safe.

"It is an absolute furphy that individual states can veto changes to the GST. The Commonwealth Treasurer has absolute discretion over the distribution method," Ms Giddings said.

"All Tony Abbott needs to say is that he will not try to change the current GST distribution system. And yet he has still left the door open."

Any change to the GST distribution system could adversely affect Tasmania's budget.

Ms Giddings argues that the current system gives sole license to the Federal Treasurer to distribute GST revenue, which are based on the Commonwealth Grants Commission decisions without being bound by them.

Yesterday's statements have done little to change the mind of local Labor representatives, who are running an advertising campaign that says Abbott would reduce Tasmania's GST share if elected.

Labor state secretary John Dowling said Tony Abbott "says different things dependent on what state of Australia he's in".

"We'll continue our campaign until Tony Abbott stands with [Western Australian Premier] Colin Barnett in Hay Street Mall in Perth and unequivocally commits to the current system," Mr Dowling said.

Franklin Labor MHR Julie Collins said Mr Abbott "can't be trusted because he says some states should get more, but others won't be worse off".

"This is not possible - the GST pie is only so big," she said.