Opposition frustration is mounting over any signs of progress on a top level inquiry into the Government's controversial Saudi sheep deal, and the Greens are miffed at getting mixed messages.

It's been well over a year since an Auditor General investigation was launched, but the Green Party has had no joy finding out where it's at.

Co-Leader James Shaw said he respects the right of the Auditor General's office not to give updates on its investigations.

But he thinks it's frustrating it can't say what progress there has been, while the Government refuses to at the same time.

"It raises suspicions that the process is somehow being manipulated by the government to protect (Foreign Minister) Murray McCully, and Cabinet in a wider sense."

The Greens have asked both the Prime Minister and Foreign Minister Murray McCully whether they've received any information on the timing, or substance, of the Auditor General's inquiry into the matter.

The Prime Minister's response is that he's received no information but Mr McCully said it wouldn't be consistent with the public interest to provide the information until the Auditor General's inquiry has concluded.

Green Party Co-Leader James Shaw said that's demonstrating wilful ignorance.

"I think what he means by that is that it's not in his interest to talk about the report."