The government will also adopt Labor's tobacco tax hike of 12.5 per cent per year for four years - as foreshadowed by Fairfax Media last month - which according to the Parliamentary Budget Office will raise $3.8 billion over four years, and $47.7 billion over 10 years. Prime Minister Malcolm Turnbull and Treasurer Scott Morrison in the Prime Minister's suite on Monday morning, budget eve. Credit:Andrew Meares But in a major blow to the opposition, Treasury modelling of the tobacco tax hike - which will be included in the budget papers - has called into question Labor's claim the increase will pay for its funding promises, finding that it will only raise $2.3 billion over four years, and $28.2 billion over 10 years. That, in effect, blows a $19.5 billion hole in the opposition's policy costings on election eve and will put pressure on the opposition to find additional savings or raise extra revenue. Late on Monday night, Labor treasury spokesman Chris Bowen accused the government of a "desperate attempt to cover for the fact the government will be adopting, in full, Labor's policy on tobacco excise".

He conceded the revenue assumptions would be updated and stressed it had never been tied to Labor's school funding plans. Treasurer Scott Morrison during question time on Monday. Credit:Andrew Meares The trio of new multinational tax avoidance measures build on the Coalition's first set of multinational anti-avoidance laws, which was passed last December and will raise an estimated $700 million in the first year through stopping companies artificially structuring themselves to move profits to low tax countries. Taken together, government sources said they expected the two tranches to raise more money than Labor's competing tax avoidance laws, which are designed to raise $2 billion over four years. Illustration: Ron Tandberg.

The changes mean both major parties go into the election advocating a crackdown on multinational tax avoidance, but the similarities do not end there. The Coalition's tightened superannuation concessions are unlikely to blunt an attack from Labor, which is gearing up for an assault on the pre-election budget as a boon for the well-off, while giving nothing to the majority of low and middle-income earners. Fairfax Media revealed on Monday that a company tax cut would be introduced in the budget, while changes to the second top tax bracket of 37¢ in the dollar are also expected, as is an end to the deficit repair levy imposed in 2014 on the highest income earners. Other measures include an extra $1.2 billion for schools, $2.9 billion for health, additional funding for corporate regulator ASIC and a possible extension of the $20,000 instant asset write-off for small business is in prospect. The government is expected to argue that between tightening super tax concessions for the wealthy and its multinational tax crackdown, its budget will meet Mr Turnbull's stated aim of promoting fairness, while also stimulating jobs and growth.

Also in the budget is a replacement scheme for Labor's Low Income Superannuation Contribution scheme, which pays up to $500 to the accounts of people earning under $37,000 a year. The government still intends to wind up that scheme but, in a change of heart, will now replace it with another benefit, which a source said would remove the cost-penalty to the low paid when they pay income into superannuation accounts. This is expected to be beneficial to low-paid workers, the majority of whom are women. In Parliament on Monday, the opposition attacked the government over what it said were plans to cut taxes for multinationals and for the top 1 per cent of earners while leaving workers earning less than $80,000 a year out in the cold. "Data from the Australian Tax Office shows that four out of five Tasmania workers earn less than $80,000 a year. So why is the Prime Minister giving large multinationals a tax cut at the same time as leaving four out of five Tasmanian workers with absolutely nothing?" shadow treasurer Chris Bowen asked. But Mr Turnbull fired back that the budget would be "responsible, fair and prudent" and would outline changes to the tax system, to make it "more sustainable, fairer and set us up for the 21st century for those great economic opportunities that await us". Mr Morrison hammered home the point about fiscal rectitude and that "this is not a time to be throwing money around: you have to spend money wisely, you have to target it and the ultimate test is will it drive jobs and growth. We'll afford the things that need to be afforded in health and education and we have made our commitments plain there."

On Sunday, Mr Morrison had said the budget would offer tax relief for "people out there earning average wages"; he clarified on Monday that "the average full-time earnings in Australia is $80,000". Tax stats from 2013-14 show there were 9,712,293 Australians with taxable income and 7,187,104 of them earned less than $80,000. The multinational tax avoidance measures have been developed over the course of the last year after Australian Treasury officials went to Britain to work with their counterparts and understand how that country implemented the so-called Google tax. Mr Morrison was handed a report by his officials in February that set out options for tackling multinational tax avoidance. In Britain, the Google tax targets multinational companies that avoid paying tax by shifting thier profits to lower taxing countries, in that case Ireland. In Australia, numerous companies have been identified as using so-called "marketing hubs" such as Singapore to reduce their taxable profits in Australia.

And for the first time, the budget will put actual dollar figures on how much will be raised via the first and second tranche of tax avoidance measures. Follow us on Twitter Follow James Massola on Facebook