The debate between the treasury spokesmen capped a week in which the economy dominated debate and which saw Mr Morrison embarrassed over an $18 billion error in his claim of a $67 billion Labor "black hole". Scott Morrison and Chris Bowen went head to head in a debate on Friday. Credit:Alex Ellinghausen However, the attack over ALP costings successfully flushed out the opposition's plans to dump $9.2 billion of promises to keep the Schoolkids Bonus, reverse changes to the pensions assets test and not restore aged care funding and had Bill Shorten ducking questions on Friday. The Reachtel polling surveyed 2700 people across Australia, was conducted on Thursday evening and the 4 percentage point lead for Labor is the first time the opposition has led in this poll in 2016. Mr Turnbull has a commanding 54.9 per cent to 45.1 per cent lead as better prime minister in the poll, and 29.2 per cent of voters nominated economic management as the most important issue to decide their vote - nearly double every other issue, including health, education and border protection.

Last week's Fairfax/Ipsos poll had the Coalition ahead 51-49 on the two-party preferred vote, while Newspoll had Labor leading by the same margin. Sunday's debate in Canberra between the Prime Minister and the Opposition Leader would normally mark the starting point of a five-week campaign and comes after an at times fiery debate between the party's chief economic spokesmen on Friday. Mr Bowen went on the attack early, warning Australia's Triple A credit rating was under "great pressure", questioning key budget forecasts underpinning the return to budget timeline of 2020-21, and lamented the Australian dream of home ownership was slipping away. But Mr Morrison gave as good as he got and pinned down the Labor challenger on the ALP's decision to dump a pledge to keep the Schoolkids Bonus. The Treasurer highlighted the Coalition's budget plans to cut company taxes to 25 per cent over the next 10 years, expand the middle-income tax bracket, crack down on multinational tax avoidance and tighten superannuation tax rules.

On the deficit forecast he said that "you can't pay for things, as much as you would like to, with money that isn't there. Having something costed is not the same as having something funded. I can know the price of something, but it doesn't mean I can afford it. We can afford what is in our budget," he said. Asked if the spending cuts and fiscal repair measures unveiled in the budget this month were enough, Mr Morrison said "no, that's why we need to continue down that path when and if we are re-elected", a comment Labor seized on as proof more cuts to health and education were coming. Mr Bowen promised before the end of the campaign Labor would release details of the impact on the budget [of] announced policies over four years and a decade. "We'll include a credible pathway back to balance and the year it would be achieved. My challenge to the Treasurer today is this: do the same ... they should reveal the 10-year cost of their promises," he said. He also called on Mr Morrison to admit the Triple A credit rating was under pressure, and labelled iron ore, nominal growth and wages forecasts "heroic".

Regardless of who was treasurer on July 3 "we'll be told the same thing, the rating is under great pressure". But Mr Morrison fired back that the budget repair "would be easier if the opposition wasn't continuing to block $18 billion in savings measures". "The previous government promised a surplus 650 times ... I'm not going to do that. I will be honest with the Australian people." And he landed blows on Mr Bowen over how, and when, the ALP decided to dump $9.2 billion in promises and over Labor questioning how nearly $50 billion in company tax cuts would be funded - but banking the money anyway.