The Government is going to change the law so employers cannot pay less to employees in the KiwiSaver scheme than to those who are not.

Labour Minister Trevor Mallard said the Government would amend the Employment Relations Act to ensure employers met their obligations to pay contributions to their employee's KiwiSaver accounts.

"This will address the situation that has seen some employees paying their employer's contribution to their KiwiSaver account out of their own salary.

"I have had reports of employers paying KiwiSaver and non-KiwiSaver members differently, and the Government intends to clearly specify that this sort of behaviour will be illegal," Mr Mallard said.

He said the issue had originally been left to employers and employees to agree to in their employment agreement negotiations on the understanding that employers would take the extra costs into account across the entirety of their workforce..

"This clearly hasn't happened ..... there is no way that it is fair for one employee to be paid less each week in their take home pay than an employee doing the same tasks, simply because they choose to be in KiwiSaver and the other employee doesn't."

He said the law changes would not affect employers' eligibility for the employer tax credit, and employers and employees would still have to operate within the good faith bargaining framework in the Employment Relations Act.

The law change would come into force on the date the amendments are introduced to the House, but would not effect employment agreements already entered into before that date.