Treasury secretary Ken Henry declined to give any detail about the tax assumptions when quizzed on a Senate hearing Tuesday.

"My understanding is that the treasurer will shortly be putting more information into the public domain," he said.

Coalition senators are eager to settle from where the $10.5 billion in forecast revenue from the minerals resource rent tax and expanded petroleum resources rent tax will originate.

Dr Henry, in an earlier appearance, took 13 inquiries on notice and depended on a public interest immunity to keep information.

Liberal chairman of the Senate committee Mathias Cormann suspended proceedings shortly to let Dr Henry ask Treasurer Wayne Swan again if he could react to the unanswered queries.

When the hearing resumed, Dr Henry said he had spoken to Mr Swan's staff and repeated the treasurer's plan to release the information "imminently".
At this stage, the government is still drafting the details and information had not been finalised.

The information would "allow the reader to determine how much of the net revenue impact of the July 2 announcement is due to parameter variations, including commodity prices, and how much is due to policy decisions," according to Dr Henry.

He had no knowledge when the information would be announced or in what form.

"I am really sorry for the position the government has put you in, quite frankly," Senator Cormann said, not blaming Dr Henry for the situation.

Mr Swan is expected release imminently more detail on the assumptions supporting Labor's proposed resources rent tax.

The federal government has been criticised for altering as commodity prices, commodity volumes, the exchange rate and other assumptions between the May budget and the announcement of a revamped resources tax on July 2.