South Australian Premier Jay Weatherill has apologised over a tweet which falsely claimed a federal Liberal MP was in Fiji rather than campaigning for his seat in Adelaide.
Mr Weatherill has admitted the Twitter account involved in the attack on Boothby MP Andrew Southcott was held by a state government ministerial adviser.
The premier said he contacted Mr Southcott on Tuesday to apologise.
"Mr Southcott was angry and he's entitled to be because lies were spread about him," the premier told reporters.
"It's unacceptable and I said so."
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But Mr Weatherill said he did not consider the staffer's actions a sacking offence.
He said staff on both sides of politics regularly used Twitter traffic to "bag each other".
"I think it's something that should stop," he said.
"That's why I apologised directly to Mr Southcott. But make no mistake it happens on both sides."
The tweet in question asked for confirmation that Andrew Southcott was in the country, adding: "been told and seen on here that he in Fiji for next 10 days".
Mr Southcott said the tweet was designed to damage him.
"It's certainly a false claim and it's very important if you're going to make a claim that you've got to be able to back it up," he told ABC radio.
"If you're going to publish something which is false and designed to damage, well, you've got to be held accountable for that, especially if you're in a position of responsibility."
Mr Southcott said the last time he was in Fiji was when he was 10 years old.
He holds Boothby, in Adelaide's southern suburbs, by just 0.6 per cent.
Coalition frontbencher Christopher Pyne later named the government adviser as Tim Picton who works in the office of South Australian Health Minister Jack Snelling.
Mr Pyne said Mr Picton's actions exposed Prime Minister Kevin Rudd's promise of a new, positive approach to political campaigning as an insincere con.
"Mr Rudd needs to explain if he thinks it's appropriate for Labor campaign operatives to tweet lies about Liberal candidates," he said.
"If not, what action will he take to discipline the staffer concerned?"
