Queensland has lost its Arts Minister and Transport Department head in the same day.

Minister Ros Bates resigned from cabinet for health and family reasons.

Four hours later, Premier Campbell Newman sacked Transport and Main Roads Director General Michael Caltabiano.

The former Liberal MP is at the centre of an Ethics Committee and Crime and Misconduct Commission investigation into an alleged nepotism scandal.

The son of Ms Bates was given a plum job in Mr Caltabiano's department and he's accused of misleading parliament to cover up their work history.

Mr Caltabiano stood aside in October on full pay and has been pocketing almost $10,000 a week before tax.

Mr Newman didn't want to comment on Mr Caltabiano's dismissal, but said he was saddened to see Ms Bates resign.

She is the third minister to go in just 10 months, and her resignation could spark a widespread cabinet reshuffle.

Mr Newman said he did not ask her to quit; but he didn't ask her to stay on either.

"She has been under intense pressure," he said.

"Ros has done an outstanding job under difficult circumstances.

"I think she goes now with her head held high."

Ms Bates' career has been plagued by controversies which often overshadowed the work of the government.

She had been under fire for months over the nepotism claims and had failed to fully disclose all contact with lobbyists.

She's also spent 25 per cent of her time on sick or recreational leave.

Just one month ago, she stared down her opponents and proclaimed she'd be a long-term minister: "I am the captain of the ship and the ship still sails."

But it appears as though relentless opposition questioning over her integrity wore her down.

Mr Newman insists Ms Bates "came up trumps" during Question Time but the opposition says they still want answers on her contact with lobbyists.

"Perhaps there is more to come out," Opposition Leader Annastacia Palaszczuk said.

Ms Palaszczuk said Mr Newman failed to show leadership and should have fired Ms Bates and Mr Caltabiano months ago.

Australian Catholic University political analyst Scott Prasser says it would have been more damaging to keep Ms Bates on than to have her leave.

Attacks would have kept on coming because Ms Bates was unwilling to acknowledge her mistakes, he said.

Mr Prasser said the community can have confidence however that there was an improved sense of accountability with the Newman government.

No heads rolled in the former Labor government over the Queensland Health payroll debacle.

Mr Newman says he'll consider using Ms Bates' resignation as a chance for a wider cabinet reshuffle.

He maintains that the three ministerial resignations don't reflect poorly on his government.

"People have seen this government's performance when it mattered, during the recent floods," he said.

"They understand this is a government that has a great team and is showing the leadership to take the state forward."

Education Minister John-Paul Langbroek will act in Ms Bates' role until a replacement is found.

Mr Caltabiano's contract will be terminated on March 15.