Opposition Leader Tony Abbott says he's not afraid of Peter Beattie but Kevin Rudd should be.
Mr Beattie, Queensland premier from 1998 to 2007, will run for Labor in the federal seat of Forde at the September 7 election.
Labor believes the southeast Queensland seat held by Liberal Bert Van Manen is winnable, given its margin of 1.6 per cent.
They also hope Mr Beattie's comeback will lift its chances across the state.
When Mr Beattie left politics six years ago, he vowed never to return.
"There would be a state funeral if I tried to go back into politics: mine. Heather [his wife] would kill me," he said at the time.
Mr Abbott told reporters in Launceston on Thursday Mr Beattie is a potential leadership rival for the prime minister.
"Another flim-flam man who hit people with record debt and deficit, who is just going to add to the leadership instability in the Labor party," Mr Abbott said of the former premier.
"You might say to me 'Am I worried about Peter Beattie?' Of course not, but I bet Kevin Rudd is."
Earlier, Mr Abbott described Mr Beattie as a "last minute celebrity blow in".
Opposition Leader Annastacia Palaszczuk says the taunts and the dominance of debate about the former Beattie government in question time proved the LNP was worried.
She says he'll absolutely win.
"He is one of the best campaigners the state has ever seen," she said.
"I know he will be out there working every day, night and day, to earn the trust of voters down in Forde.
"It will definitely boost federal Labor's chances here in Queensland.
A year ago Mr Palaszczuk said it had never crossed her mind Mr Beattie would make a comeback.
"Anything is possible in Queensland, especially Queensland politics, and especially when Peter Beattie is involved."
Meanwhile, Trade Minister Richard Marles said Mr Beattie's return is very exciting news.
"Peter Beattie is one of the most formidable politicians that Labor has in this country," he told Sky News.
"In a seat like Forde he's going to make a real difference."
Former Queensland treasurer Terry Mackenroth also says Peter Beattie's decision to run as a candidate in the seat of Forde at the election will boost Labor's chances.
"I think people still think Peter Beattie did a pretty good job as premier of Queensland. I'm certain when people decide who they're going to vote for, they'll look at the job he did and that will help him."
Treasurer Chris Bowen says he welcomes Mr Beattie's return to high-level politics.
"Peter does bring I think a very great addition. Of course, Kevin being from Queensland, the prime minister being from Queensland...is a wonderful thing."
