Opposition Leader Tim Nicholls says Sam Cox's defection to One Nation is selfish.
News broke on Saturday morning that the former LNP member for Thuringowa had jumped ship to One Nation and would contest the seat of Burdekin in north Queensland.
One Nation senator Pauline Hanson posted a welcome to Mr Cox on Facebook, saying he would be "a powerful voice for the people of the Burdekin".
However, Mr Nicholls wasn't impressed.
"This is all about Sam Cox's political interests, not about representing Queenslanders," he said.
Mr Nicholls said after Mr Cox lost his seat of Thuringowa and failed to be nominated for another seat, he decided "seat-hopping" was the way to get himself into Parliament.
One Nation also lost the candidate for Bundamba earlier in the month when Shan Ju Lin was disendorsed, following a since-deleted Facebook post stating gay people engaged in "abnormal sexual behaviour" and "should be treated as patients".
Another candidate, Andy Semple, withdrew in late December after he was asked by the party to delete a controversial tweet.
Mr Nicholls said the fact that One Nation had completed the "hat-trick" showed they were not a serious political party.
"Governing is serious business, you need serious people with serious plans. You can't just whinge and complain," Mr Nicholls said.
"One Nation is more interested in themselves ... than they are about Queenslanders."
Mr Nicholls didn't rule out forming a Coalition with Ms Hanson's party, but said it's "not on our radar screen".