The Business Day newspaper reported on Thursday.
AMCU's position appeared to dash hopes that new Mines Minister Ngoako Ramatlhodi, who had thrown his weight behind mediation efforts, might be able to break the deadlock between the strikers and platinum producers.
"The government proposal was not a new proposal. They introduced (an old proposal) that has already been rejected by our members three months ago," the newspaper quoted Association of Mineworkers and Construction Union president Joseph Mathunjwa as saying.
He added the union was maintaining its demand for a salary increase to 12,500 rand ($1,200) a month.
About 70,000 AMCU members downed tools in January at Anglo American Platinum, Impala Platinum, and Lonmin in a strike that has hit 40 percent of global production of the precious metal used for emissions-capping catalytic converters in automobiles.