A former member of Campbell Newman’s government has spoken about his concerns for democracy ahead of a weekend by-election for his seat.

An MP who quit Campbell Newman’s government says trust will be a major issue for voters who’ll elect his successor on Saturday.

Political commentators say Mr Newman’s Liberal National Party is unlikely to retain the Brisbane-based seat of Stafford, formerly held by Dr Chris Davis.

Dr Davis quit parliament in May, saying he couldn’t support changes that might undermine democracy in Queensland.

He attacked the government’s decision to dramatically increase the amount people can donate to political parties in secret.

He also expressed concern that bipartisan support is no longer considered necessary when appointing the head of the state’s corruption watchdog.

Dr Davis used a radio interview on Thursday to remind voters why he walked away from the LNP and from parliament.

He said he felt he had no option but to force a kind of mini-referendum on the changes to electoral donation laws, and the Crime and Corruption Commission.

“I could have (stated the concerns in parliament) but I was encountering an enormous amount of hostility in speaking out on those issues,” Dr Davis said.

“They were not … trivial matters. They were issues that get to the heart of our democracy, that caused a lot of grief in Queensland in previous years.”

He said he didn’t want to be part of any “perception that we were not always putting the public interest first”.

“So, I felt it necessary to go back to the electorate and ask them to have a say on what was really important,” Dr Davis said.

“Who do they trust and why do they trust them, both the individual and the party they represent.”

Dr Davis would not say which way he’d be voting on Saturday.

He said he hasn’t spoken to the premier Mr Newman, who holds the neighbouring electorate of Ashgrove, since he quit the parliament.

“I don’t think that would be helpful. I was fired (as assistant health minister) for my stand on these matters and I think that probably gives some indication of how far apart we were on these particular issues.”

He had a final parting shot for the premier, when asked if his leadership style was a problem.

“I think there’s a whole style of politics that could be a lot better,” Dr Davis said.

“I never got the perception that we had great statesmen present in this state of Queensland, and I think we’re the poorer for that.”

Mr Newman did not directly respond to Dr Davis’s comments.

But he told reporters the LNP’s Bob Andersen was the “underdog candidate” in Stafford, despite being part of a strong team with a great plan for Queensland’s future.

He wouldn’t say if he’d view Saturday’s result as an indication of how things might go for the LNP at next year’s state election.