ACTU president Michele O'Neil will describe the peak body's proposed $43-a-week increase - almost double the amount awarded last year - as "modest" when she addresses the Fair Work Commission's wage panel on Wednesday.

The language reflects that used repeatedly by Mr Shorten, who on Tuesday repeated his position in favour of a "modest but meaningful" wage rise for 2.3 million Australians.

Mr Shorten has pledged to tear up the Morrison government's submission to the annual wage review and replace it with Labor's own "bold" submission if he takes power on Saturday, but would not name a figure when asked if he supported the ACTU target.

Ms O'Neil, who will be the first ACTU president since Bob Hawke in the 1970s to personally push the union's case before the commission, will tell the wage panel that the ACTU's initial claim for 6 per cent in 2019-20 is "a modest proposal" needed to pull low-income workers out of poverty.

"Despite a decade of economic growth - including some years of double-digit growth in profits - the proportion of workers who are paid the lowest they legally can be paid for their work has drifted ever upwards," she will say on Wednesday.

"It is hard to think of any better example of how trickle-down economics has failed working Australians."

The union peak body, which is bank-rolling a multimillion-dollar advertising campaign to unseat the Morrison government at Saturday's election, is pushing for Labor to adopt its policy to increase wages by 11.5 per cent over two years.

That would bring the national minimum wage - currently $18.93 an hour, or $719.20 per week - in line with its "living wage" target of 60 per cent of median earnings, up from 54 per cent.

Employers argue that such an increase would impose a heavy burden on small business owners, and could drive up unemployment and damage the economy.

Defending his plan to make a fresh Fair Work submission without first seeking detailed modelling from government advisers or consulting with stakeholders, Mr Shorten said while the decision was "unprecedented" it was necessary in a time of "chronic wages stagnation".

He said the amount of the increase would be "up to the Fair Work Commission", while adding that previous wage increases had failed to keep up with the cost of living.

"I don't think that an adult trying to make ends meet, should be working for an hourly wage that doesn't take them out of poverty," Mr Shorten said while campaigning in Burnie, Tasmania on Tuesday.

"What we want to do is just get wages moving again, but we will take on board, in our submission, even before Fair Work makes a decision, the arguments about business and industry capacity to pay, staged implementation."

He dismissed the Morrison government's submission to the annual wage review as "meaningless, insipid".

The Coalition used its submission, lodged last month, to argue that Australians on the minimum wage were already earning a "living wage", according to the benchmarks adopted by the United Kingdom, which took part-time as well as full-time employees into account.

Labor has promised to legislate to enable the commission to set a long-term "living wage" target but is unlikely to achieve this before this year's wage ruling - expected to take effect from July 1 - creating a narrow window for it to act if it wins the election.

The commission set a deadline of March 15 for submissions but would be expected to accept a new submission from the government if a new prime minister was elected this Saturday.