Unions have projected a $50-a-week rise in the minimum wage will create as many as 57,000 jobs in the first year after being introduced.

The Australian Council of Trade Unions' projections rely on two methodologies outlined in a reply submission to the Fair Work Commission's annual wage review.

They say between 40,000 and 57,000 jobs will be created a year after the minimum wage is lifted by $50 a week, with a further 27,000 to 30,000 in the second year.

"When people on lower wages get a pay rise they spend it in the local economy, and that creates more jobs," ACTU secretary Sally McManus said.

The union peak body wants a $50 wage boost for the nation's lowest-paid workers.

But employer groups have warned that figure would reduce the job security of low-paid workers and lower employment opportunities.

Treasurer Scott Morrison said the union movement was a "closed shop" that catered only for people who were already employed.

"We've got a plan for stronger economy, unions just have a plan for stronger union bosses," Mr Morrison told reporters in Geelong.

He said jobs were created through backing business to invest.

Ms McManus said the Turnbull government and business lobby were trying to keep wages down by running a scare campaign against higher wages.

"That's the same discredited, untruthful, damaging trickle-down economics this government loves to roll out," she said.

The projections have been released as the ACTU's Change The Rules campaign gets into full swing following a major rally in Melbourne earlier in the week.

The demonstration on Tuesday kicked off a series of marches across the country in April and May as part of the biggest campaign since the "Your Rights At Work" push in 2007 that helped bring down Work Choices and the Howard government.

The first projection uses information about households of people on low incomes, while the other relies on Treasury assumptions which calculate the multiplier effect of a wage rise.

The Fair Work commission's decision on the latest minimum wage increase will take effect from July 1.