BHP is facing a push from politicians and heavyweight unions to scrap plans that would permanently prevent mining at its Mount Arthur project from the end of the decade, calling on the resources giant to allow other operators onto the site in the heart of the coal-rich Hunter region.

The push, from Nationals MPs in the region and the mining union, comes two weeks before a deadline for the NSW government to decide whether to approve the plan to end mining at the site near Muswellbrook by 2030.