The letter was sent by Treasury official Ian Beckett on June 26 in response to the FOI request for "copies of any submissions from the Treasury to the Treasurer in relation to varying superannuation tax concessions".

The letter, dated June 26, lists four submissions from Treasury to Mr Hockey this calendar year. They were dated January 29, March 6, April 21 and April 22. It is believed the final submission was Mr Hockey requesting Treasury run the ruler over Labor's proposal.

Mr Bowen said on Tuesday that the letter was "proof that the Prime Ministerial-chaired expenditure review committee was actively considering changes to superannuation tax concessions right up until Labor announced it plans for fairer superannuation tax concessions".

"Then Tony Abbott decided that political opportunism should trump good policy."

'Possible policy options'

In explaining why he would not give Labor the details of the four submissions, Mr Beckett said "all documents are deliberative in nature containing preliminary examination of possible policy options prepared early in the 2015-16 budget process for potential consideration by a committee of cabinet".

"The issue of superannuation and taxation concessions is complex and of considerable sensitivity.

"I also find it is important that the government and the Treasury retain the ability to freely discuss options in the development of policy, and am of the view that disclosure of the material would prejudice the confidentiality necessary for negotiating and developing advice in relation to superannuation."


Despite the government having slammed the door on super tax changes, Mr Beckett said the "premature release" of the documents "would constrain the consideration of these issues and would adversely impact the policy development process".

'Possible consideration'

Mr Beckett said "one of the documents was prepared for possible consideration by a committee of cabinet in the lead-up to the 2015-16 budget".

"Therefore consider that it is of close contextual proximity to cabinet and that release could potentially impair the confidentiality of cabinet processes."

A spokeswoman for Mr Hockey was tight-lipped on the details of the submissions but said it was possible Treasury prepared options as part of the pre-budget process without being specifically requested to do so. She noted Mr Bowen had written in his own book in 2013 that sometimes Treasury prepared such options

Mr Bowen said the government should release the submissions "as a matter of urgency".

"If the Abbott government truly has nothing to hide on plans to change super tax concessions then there should be no problems releasing these documents," he said.

"The Prime Minister just can't be trusted on superannuation. We know the Treasurer originally wanted a 'national conversation' that included considering super tax concessions."


'No changes'

Two weeks ago, Prime Minister Tony Abbott and Mr Hockey reconstituted the retirement income inquiry in return for the Greens agreeing to pass $2.4 billion in pension cuts. But they stressed at the time the review would be meaningless because there would be no changes to super this term or the next. Mr Abbott re-emphasised this on Saturday in his address to the Liberal Party Federal Council.

"We won't increase taxes on superannuation or increase the restrictions on superannuation because your retirement savings belong to you and not the government," he said.

After the tax discussion paper was released, a consensus for change developed rapidly. Mr Hockey said "we are well prepared to work in a bipartisan manner with Labor to have real reforms of the taxation system".

But Mr Abbott made some pointed comments that undercut the Treasurer and the day after the budget was delivered, Mr Hockey announced the dumping of the retirement review and the hardened stance against super tax change.

Labor has pledged that if elected, it will impose a 15 per cent concessional tax on super earnings above $75,000. It will also lower from $300,000 to $250,000 the income threshold at which the 30 per cent rate applies to super contributions.