Opposition Leader Bill Shorten pressed both energy prices and hospitals as he launched the ALP's campaign for the crucial seat of Longman on Sunday.
Mr Shorten spoke to the party faithful along with Labor candidate Susan Lamb, whose resignation over dual citizenship triggered the poll.
Ms Lamb said the fight for the seat is going to be tough.
"There are people we still need to convince and there are votes we still need to win - friends, together I know we will win because we are not done yet but I tell you what, Longman is done with Malcolm Turnbull."
Mr Shorten said voters shouldn't be fooled into handing a protest vote to One Nation.
"You are not protesting, you are being used to send a vote to the LNP and what you will get with that is you will get the cuts to schools and hospitals and TAFE - you'll end up seeing fewer apprenticeships, it harder for working class kids to go to university and the pension and the penalty rates will go backwards."
The federal opposition's latest pledge is to spend $1.4 billion over five years to keep in place the energy supplement for pensioners and welfare recipients.
Queensland Premier Annastacia Palaszczuk (left), ALP candidate for Longman Susan Lamb (centre) and Federal Opposition Leader Bill Shorten (right). Source: AAP
Draft laws to scrap the supplement for anyone who's become a new pensioner or allowance recipient since September 20th, 2016 are currently before the parliament.
Axing it would mean a cut of more than $14 a fortnight to single pensioners or around $365 per year.
Mr Shorten said at a time of rising energy prices, the last thing pensioners need is a cut to their household budget.
But speaking in Townsville, Mr Turnbull said only the Coalition can keep power prices down.
"It shows Bill Shorten's desperation and you know what it does? It shows he's given up on bringing down energy prices. It shows - what that is, that is a surrender by Bill Shorten of any commitment to keep electricity prices down," he said.
"He has a plan to force-feed - without any engineering or economic consideration - force-feed renewables into the system in a way that will force up electricity prices."
Meanwhile, the latest ReachTEL poll shows Ms Lamb's chance of winning Longman is in doubt with LNP candidate Trevor Ruthenberg predicted to snag 51 per cent of the vote compared with 49 to Labor on a two-party preferred basis.
Mr Shorten admitted it will be an uphill battle.
"It is a tough fight. We are the underdogs. The bookmakers have the other mob as the favorites and now of course the LNP and the One Nation political party have teamed up again and are swapping preferences just to try to knock us - the underdog off from winning."
Cabinet Minister Josh Frydenberg told the Nine Network he still believes the Coalition has the superior candidates in the five by-elections.
"So it's really, really difficult, it's like climbing Everest, but we can do it, we have terrific candidates."
