Four months ago Joe Hockey was trying to balance the federal budget using an iron ore price of about $60 a tonne.

Now the Treasurer is warning of a revenue loss of $25 billion over four years, as he factors in a price as low as $35 a tonne.

“There seems to be no floor,” Hockey told The Australian Financial Review on Monday, four weeks out from delivering his second budget.

But the government won’t be chasing down the revenue loss, opting instead to pursue growing export opportunities in Asia.

Despite the bleak outlook for revenue, Prime Minister Tony Abbott continues to promise the May 12 budget will be good news for families and small business.

“The assurance that I give you is that we aren’t going to tackle our budget problems at the expense of families’ budget problems,” he told the Seven Network.

The discipline of the government’s first budget meant families and small business could expect good things from the second.

Labor, which faced similar revenue write-downs in government, is not blaming the treasurer for the predicament created by slumping iron ore prices.

But shadow treasurer Chris Bowen criticised Hockey for creating unrealistic budget expectations.

A Fairfax-Ipsos poll, published on Monday, also shows voters are not impressed with the treasurer as he beavers away at the budget.

He has suffered a 45 per cent reversal in his approval rating during the past 13 months from plus 20 per cent in March 2014 to minus 25 now.

Yet voters still say the Coalition is the better economic manager at 41 per cent to Labor’s 32.

Asked about the fall in his approval rating, Hockey said it was his job to “level” with the Australian people about the mess the government inherited from Labor.

“It’s not about me, it’s about what is right for Australia,” he said .

The Ipsos poll show six out of 10 voters (58 per cent) say they still want the budget deficit addressed as a “high priority” and a growing number favour an increase in the 10 per cent goods and services tax.