The by-election for the Queensland state seat of Redcliffe, north of Brisbane, will be held on February 22.
The seat became vacant after former LNP member Scott Driscoll quit parliament in November because he was found guilty of misleading the house about his financial and business interests.
He had already quit the party, having moved to the parliamentary crossbenches, in April 2013 when the allegations surfaced.
Premier Campbell Newman announced the by-election date on Monday after touring the Redcliffe Hospital.
He apologised and pleaded with voters to not judge the LNP for Mr Driscoll's failures.
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Registered nurse Kerri-Anne Dooley will represent the LNP at the Redcliffe by-election.
Labor's candidate is former federal MP Yvette D'Ath.
Mr Newman said the LNP would be the underdog because of Mr Driscoll.
"There'll be people on the (Redcliffe) peninsula who are angry," he told reporters.
"Well, we are all angry about what happened but that's not a reason for a protest vote, which I'm sure the other side will be urging."
Mr Newman said February 22 was chosen to give voters four weeks after the holiday season and time before the campaign proper began after Australia Day.
Ms Dooley, who ran for the Family First Party during the 2012 state election, said she supported the LNP's policies and was impressed by what the government had achieved.
She also admitted she may receive a backlash because of Mr Driscoll's legacy.
"The anger and grief of the community is the reason why I put my hand up," she said.
"I want to be the strong, local, passionate voice to deliver with the Newman government what we can for the people of Redcliffe."
Mr Newman also ruled out speculation there would be an early general election.
He vowed he would serve his full term and call an election next year.
