Coles and the conservative shop assistants' union are teaming up to avoid a repeat of last year's embarrassing legal ruling that found many supermarket workers were being underpaid.

On Thursday, lawyers for both Coles and the Shop, Distributive & Allied Employees Association (SDA) attempted to prevent the Fair Work Commission's full bench from hearing the latest challenge to one of their deals.

Lawyers for the supermarket giant argued it would not be "in the public interest" to escalate the case.

Coles has been embroiled in an underpayment scandal for two years after Fairfax Media revealed its most recent union deal had collectively left workers tens of millions of dollars a year worse off.