Employers have warned against hiking the minimum wage after Opposition Leader Bill Shorten indicated his willingness to bow to union pressure for a "living wage", saying forcing business owners to pay more would only drive up the unemployment rate.

In a speech delivered to business leaders on Wednesday, Mr Shorten declared that the coming federal election would be "a referendum on wages" and that the current $18.93 minimum hourly pay was based on an outdated understanding of the cost of living.

Bill Shorten has indicated that he may bow to the ACTU's demand for a 'living wage'. Credit:Louie Douvis

"It came in as a principle before we had mobile phones, before we charged for water, the internet hadn't been invented," Mr Shorten said.

"The minimum wage is nowhere near adequate as a living wage."