Labor is unashamedly defending its plans to permanently expand the size of government with a 10-year budget plan that embeds a record tax take to fund a surge in spending that began during the boom years.
However, analysis by The Australian Financial Review of the tax and spending projections of both sides of politics indicates the Coalition is almost certain to match Labor's spending levels unless it ramps up cuts or succumbs to the draw of higher taxes.
Failure to trigger either of those options would give a Coalition government little hope of meeting its promise of meaningfully reducing debt and deficits, the analysis shows. 
Economist Saul Eslake, who confirmed the Financial Review's calculations as credible, said voters were being offered the starkest choice about the size of government since 1993, even though in real terms the differences are modest.
While he said there was no statistically significant global evidence to support the idea that the magnitude of government has any bearing on economic growth, it was still clear that neither side has been "wholeheartedly" honest about the affordability of spending hikes and tax cuts delivered during the Howard and Rudd/Gillard years.
"Those three governments turned temporary revenue windfalls into permanent, elevated spending commitments," Mr Eslake said. "We have to be prepared to pay for it. Labor has been more honest about that, but perhaps not honest enough."
In analysis that underscores how permanent the expansion in government spending as proportion of GDP is likely to become, the 2016 budget papers and Labor's 10-year fiscal plan released on Sunday confirm there is almost no difference between the two sides on spending, which will remain at levels normally associated with recession or economic downturns.
Under Labor, payments as a proportion of GDP will stay above 25.7 per cent though to 2026-27, when they hit 25.8 per cent, the same as where they start in 2015-16.
The Liberal-National party's spending outlook is virtually identical, with outlays edging down only slightly by 2026-27 to 25.4 per cent of GDP.
The difference by 2026-27, in today's dollars, is about $6.4 billion, or 1.5 per cent of total Commonwealth spending in 2015-16.
On taxes, the contrasts are more substantial.
Labor's tax levels will climb to a record 26.4 per cent of GDP by 2026-27 from 23.5 per cent in 2015-16. It has promised to wind back negative gearing, curb the capital gains discount to investors, and plans to keep company taxes where they are, rejecting the Coalition's planned reductions.
The government's total tax take will climb to 25.6 per cent of GDP in 2026-27, an increase worth almost $34 billion in 2016 terms, but still $12.8 billion less than Labor.
The primary reason is because the Coalition has assumed a tax cap of around 25.6 per cent from 2020-21 onwards. That figure includes income from so-called non-tax receipts such as Future Fund earnings and interest income, and implies cuts in future income taxes.
A consequence of the projections is that Labor can forecast larger, if modest, long-run surpluses, whereas the Coalition's projected windfalls of around 0.1 or 0.2 per cent of GDP are essentially rounding errors.
A spokesman for Treasurer Scott Morrison questioned the reliability of 10-year budget forecasts, saying the government doesn't provide projections beyond the four-year forward estimates period.
"Accordingly the figures you have cited can only be considered as speculative as are any of the conclusions or assessments made on the basis of these speculative calculations," he said.
Labor, which hasn't challenged the Financial Review's calculations, pointed out this week that the Coalition's outlook relies on it passing around $15 billion in so-called "zombie measures" left over from the 2014 budget, and subject to being approved by next Senate.
"Despite railing against 'debt and deficit', Malcolm Turnbull and the Liberal Party actually have no honest and transparent plan to pay down debt," Mr Bowen said.
He added that Mr Morrison had effectively ripped up the government's previous strategy of producing a surplus of 1 per cent of GDP by 2023-24.
"In fact the government's own medium-term projections for the underlying cash balance to 2026-27 clearly show the government's projected surpluses are hostage to global economic developments and further downward revisions in key economic assumptions.
"The only ways the government can achieve stronger surpluses and pay down debt, will be either to allow taxes to rise higher than 23.9 per cent of GDP or, more likely, deliver deep cuts to expenditure."
Mr Eslake said the overall size of government appears to have no real bearing on economic performance.
"Contrast Sweden, Norway, Demark and Finland, all of which have government-to-GDP ratios of over 50 per cent with Switzerland, which has a ratio similar to ours and the US's.
"You can't say that the Nordic countries have grown at a faster or slower rate than Switzerland, or have any material difference in per capita GDP."
He said there was more evidence to support the idea that the way a country taxes its people matters more for economic growth.
"If a government relies too much on bad taxes that can be more damaging than collecting a bigger amount through more efficient or less distorting taxes."