Opposition Leader Bill Shorten has ruled out passing legislation to guarantee Sunday penalty rates if he wins the election.

Key points: Greens, ACTU pushing for Opposition to safeguard against changes to Sunday penalty rates

Greens, ACTU pushing for Opposition to safeguard against changes to Sunday penalty rates Shorten says proposal "playing with fire"

Shorten says proposal "playing with fire" Labor campaign advertising promises party would "keep weekend penalty rates"

Labor campaign advertising promises party would "keep weekend penalty rates" Head to Australia Votes for more election coverage

Labor has labelled calls to legislate to protect penalty rates as "dangerous", amid calls from the Greens and union movement to protect current wage levels.

The Fair Work Commission (FWC) is expected to hand down its decision on whether to cut Sunday penalty rates to bring them in line with Saturday rates after the July 2 election.

The Australian Council of Trade Unions (ACTU) and the Greens want the Opposition to step in and safeguard the current position, and have ramped up the pressure on the day Mr Shorten has switched his campaign focus from education to jobs.

Such protection would be in the form of changes to workplace legislation or award agreements.

Mr Shorten warned the Greens their position was risky.

"They're playing with fire by proposing that a government should be able to legislate on specific penalty rate outcomes," Mr Shorten said while visiting a factory in Geelong.

"They are loading the gun for a future conservative government to pull the trigger.

"What the Government has the power to put in, a future government has the power to dismantle."

Mr Shorten said a Labor government would make another submission to the FWC to campaign to maintain the status quo.

Labor advertising promises weekend penalties will stay

Campaign advertising states that if elected, the Labor Party would "keep weekend penalty rates".

It led to an exchange on exactly what Labor's course of action would be.

Reporter: Shouldn't it say we'll do our best to keep penalty rates, we'll try to keep penalty rates ...

Mr Shorten: I'll tell you ...

Reporter: ... we'll fight for penalty rates, not we'll keep penalty rates?

Mr Shorten: I didn't mean to interrupt your statement there ... Labor will at every stage fight for penalty rates.

Labor's employment spokesman Brendan O'Connor echoed his leader's comments.

"We've made clear if elected, a Shorten Labor government would intervene," Mr O'Connor told Melbourne radio station 3AW.

Mr O'Connor has previously stated such "intervention" would take the form of a submission.

He said Labor was the only party to believe in the independence of the umpire, and said legislating in the way the Greens were proposing would give the Coalition the power to bypass the commission.

The Coalition has vowed to adhere to any ruling that cuts Sunday penalty rates.

"We respect and accept the decisions of the independent arbiter the Fair Work Commission," Finance Minister Mathias Cormann said.