A union proposing to require that employers prove their buildings are safe and carry out remedial work if they are below earthquake code says it just wants workers to be safe.

The Engineering, Printing and Manufacturing Union is to vote next month on a remit to add the requirement to its employment agreements and has not ruled out taking action if employers fail to get buildings assessed for earthquake safety.

"We are not all about to walk off the job and declare World War 3 on this issue. We want to have a dialogue with employers," EPMU national secretary Bill Newson told Radio New Zealand.

People had a right to a safe workplace, he said.

Employers told the Dominion Post the legality of any such action would have to be tested in court.

Employment lawyer Peter Cullen said the proposed clause was interesting but complicated, and the courts would ultimately have to rule on strikes.

Many employers did not own the buildings they worked in, so the clause could target the wrong people, the Northern Employers and Manufacturers Association said.

Employment services manager David Low said most employers cared about their workers and did not want to put them at risk.

"We've been through the experience of Christchurch and we've got to do the right thing."

Current health and safety laws already gave strong protection for workers and a legal battle was not necessary, Mr Low said.