Peabody Energy (BTU) informed the Mining and Energy Union that it is extending the lockout of workers at the Helensburgh underground coal mine until July 6, the MEU said Thursday.

The coal mines are located on the east coast of New South Wales, Australia.

This brings the duration of the lockout to almost three weeks, in retaliation for one hour of protected industrial action by the miners in defense of fair pay and job security, the union said.

"The Mining and Energy Union is today calling on the Federal Government to reform workplace laws that allow totally disproportionate and punitive employer action in response to workers exercising their bargaining rights," the union said.

Peabody did not immediately respond to MT Newswires' request for comment.