Mr Bowen's comments came after shadow treasurer Joe Hockey said the Coalition would not rely on the official Treasury numbers to work out how much its policies cost, ahead of the federal election.

Instead, Mr Hockey said the Coalition will use the independent Parliamentary Budget Office, state government colleagues and independent advisers.

''You'll see all the details in the next few weeks,'' he told ABC radio on Friday.

''What I can say emphatically is that our numbers will be more reliable than anything the government publishes.''

Mr Bowen is expected to make an economic statement in the coming days, ahead of the Pre-Election Economic and Fiscal Outlook (PEFO) released by the departments of Treasury and Finance 10 days into the election campaign.

Until Friday, Mr Hockey had said the Coalition would release its policy costings after PEFO, after suggesting that the May budget process had been politicised by Labor. But he has now cast doubt on PEFO's independence.

''Quite clearly by flagging an economic statement the government is trying to bully the public service into a set of the numbers that clearly do not properly represent the state of the budget,'' Mr Hockey said.

''We are not going to rely on the information that is provided solely by the government because every time the government publishes a number it is dead set wrong.''

In response, Mr Bowen said the opposition was moving the goal posts on its costings and policies.

''A few months ago, it was going to be when the Treasury and Finance released their economic outlook. That in itself was too late. Now they're crab-walking away even from that commitment,'' he told reporters in Sydney.

''Last election we saw the opposition use an accounting firm which was then fined for a breach of professional standards because of the sloppy work which went into the opposition's costings. We are seeing yet again the same sloppy approach from the opposition.''

At the 2010 election, the Coalition had its costings done by an accounting firm instead of the Treasury and Finance Departments. In 2011, a tribunal found that two accountants who costed its 2010 election policies had breached professional standards.

Mr Bowen also lambasted Mr Hockey for his comments about the public service.

''I am sick and tired of the opposition trashing the reputation of Australia's public servants,'' he said. ''Australia's public servants are independent, and unimpeachable in this regard. If they prepare figures for the Pre-election Fiscal Outlook, those figures should be respected.''

This is not the first time the Coalition has questioned the independence of the public service. In the wake of the May budget, Mr Hockey criticised Treasury figures but blamed then treasurer Wayne Swan. Assistant Treasurer Mathias Cormann also suggested Treasury and Finance had been influenced by the government.

The Australian Financial Review reported on Friday that the government is facing a budget black hole of $20 billion over the next fours years.

Mr Bowen did not comment when asked about the $20 billion figure, but flagged that the budget was being hit by factors like a drop in the terms of trade.

''We'll account for all our spending, we'll account for that in an open and transparent way,'' Mr Bowen told Seven.

He said he was committed to a surplus - ''that's the plan'' - in 2016-17. Prime Minister Kevin Rudd told the National Press Club on July 11 that ''we're committed to returning the Budget to balance in 2015-16''.

On budget night in May, the government forecast a wafer thin surplus of just $800 million in 2015-16, which Mr Swan referred to as "back to balance".

There are some reports that the cabinet is divided on whether the surplus commitment should stand.

With AAP

Follow the National Times on Twitter