The Crime and Corruption Commission, which replaced the Crime and Misconduct Commission on July 1, wrote back to the Quandamooka people on October 16, 2014, saying it will not investigate the matter.

Sibelco, which paid $91,000 to mail out 98,000 letters to voters in and around the Ashgrove electorate, subsequently won by now-Premier Campbell Newman, was referred to the Crime and Misconduct Commission by Labor in June 2014.

The Ashgrove electorate in 2012 was held by Environment Minister Kate Jones, who was defeated by former lord mayor Campbell Newman.

Opposing views on extending sandmining on the island were a major public issue in 2011-12.

Labor in June 2014 also asked the CMC to investigate eight meetings between Mines Minister Andrew Cripps and Sibelco representatives between May 1 and June 19, 2013.

Sibelco subsequently presented the LNP with a ministerial briefing paper on how to re-frame the legislation to extend sandmining on Stradbroke Island*.

The Quandamooka people had one meeting with Mr Cripps before the new legislation was introduced.

On October 17, 2013, Mr Cripps introduced the new sandmining legislation to state parliament, which amended Labor's legislation that had ended sandmining earlier.

On Monday night Mr Cripps said he could not comment because the government had not been advised.

"As the Queensland government has not been formally notified of any decision it would be inappropriate to comment."

Mr Cripps has consistently defended his office's meetings with Sibelco.

In August the CCC determined Labor's complaint "did not raise a reasonable suspicion of corrupt conduct", a commission spokeswoman said.

"The CCC therefore made the decision not to investigate the matter."

The Quandamooka Yoolooburrabee Aboriginal Corporation wrote to the CCC on August 27, 2014, and then lodged a complaint on September 5, 2014, raising concerns with the CCC "about suspected corrupt behaviour" in writing.

QYAC chief executive Cameron Costello on Monday said the Quandamooka people were "surprised" the issue would not be investigated by the CCC.

"The wording that they raised was that there may be something further to investigate, but it seems like – for whatever reason – they are not going to follow that through," Mr Costello said.

"I don't fully understand why they would not take it further.

"In the public interest it would have been good to investigate fully to find out, one way or the other, whether there was any conduct that was untoward.

"However, it appears we won't find out, will we?"

"It will just be left in the air. It leaves it unresolved in the minds of Quandamooka people."

The letter back to Mr Costello, dated October 16, 2014, says the information from the Quandamooka people indicates the allegation may amount to suspect corrupt behaviour, if proven.

"Our assessment is that while the allegation you have raised may, if proved, amount to suspected corrupt conduct, the assertion of favourable treatment for Sibelco and a connection between the donations by Sibelco and the recent legislative amendments is speculative," the letter reads.

"Accordingly, the CCC is not able to take any further action."

Under the new legislation, "corrupt conduct" includes two sections – one on "impartiality" and a second on "providing a benefit to a person (or persons)", or "causing detriment" to another person.

Sibelco chief executive Campbell Jones told a state government committee in October 2013 he also met then Ashgrove candidate Campbell Newman twice before the March 2012 election.

Mr Jones in 2013 rejected suggestions Sibelco received beneficial treatment.

"We didn't get everything that we wanted," he said.

Mr Jones said Sibelco had not been returned all the land-use changes made by the previous Labor government under the new proposed bill.

A CCC spokeswoman ruled that seven questions Fairfax Media forwarded in writing to the CCC did not meet the watchdog's "media policy".

It declined to answer why the issue would not be investigated and suggested Fairfax Media run answers provided to another media outlet.

"The CCC will not confirm or deny whether it has received any other complaints or referrals relating to this issue," the blanket statement to another media group said.

"However, the CCC can confirm that its position on this issue has not changed since August.

"The CCC declines to comment further."

Mr Costello said he understood the laws had been changed since the CCC replaced the CMC.

"From what I understand, there is an additional requirement now," he said.

"Would this have been an issue if this legislation had not been changed?

"Would they have taken this issue further if this legislation hadn't been changed?

"I think that is what the public would be interested in as well."

*Correction: An earlier version of this story incorrectly said sand mining on North Stradbroke Island was extended until 2035. Although this is the stated intention of amendments to the 2011 North Stradbroke Island Protection and Sustainability Act, the legislation does not allow Sibelco to do this until it applies to renew the relevant leases in 2019. Mines Minister Andrew Cripps told state parliament on October 17, 2013: "The amendments contained in this bill will enable Sibelco to seek a renewal of mining leases in 2019 at the Enterprise mine until 2035."