The Australian Special Minister of State Michael Ronaldson has blocked the release of the source code to the Australian Electoral Commission's EasyCount software in defiance of a Senate motion, stating that the release of the source code could lead to the software being manipulated or hacked.

Last week the Greens passed a motion in the Senate calling on Ronaldson to produce source code for voting software for the Australian Senate by July 15.

The motion came after a long Freedom of Information dispute between the AEC and Michael Cordover, who had sought a copy of the software's source code in October last year, but was denied access by the AEC on the ground that the source code was considered commercially valuable to the AEC, which also runs at-fee elections for non-government authorities outside of government election periods.

Cordover appealed the decision, but found that the AEC then took the extraordinary step of trying to have him declared a vexatious applicant, thereby potentially allowing the agency to ignore all future FOI requests from Cordover.

Greens Senator Lee Rhiannon passed a motion in the Senate compelling Ronaldson to table the source code, along with all communications relating to why the AEC had asked the Office of the Australian Information Commissioner to have Cordover declared vexatious.

In a letter to the Clerk of the Senate Rosemary Laing, tabled in the Senate yesterday (PDF), Ronaldson refused to table any documents relating to the case, stating that publishing the source code could lead to the EasyCount software being hacked.

"In relation to the source code for the Senate counting system, I am advised that publication of the software could leave the voting system open to hacking or manipulation," he said.

"In addition, I am advised that the AEC classifies the relevant software as commercial-in-confidence as it also underpins the industrial and fee-for-service election counting systems."

He said that as the FOI case was now before the Administrative Appeals Tribunal, it would not be appropriate for the government to comment further.