NSW Labor environment spokesman Luke Foley has branded senior Nationals, including Deputy Premier Andrew Stoner and federal Agriculture Minister Barnaby Joyce, "deranged" over their response to the killing of a government employee by a farmer involved in a land-clearing dispute.

Mr Foley said the comments sought to "justify" or "explain away" the alleged shooting murder of environment compliance officer Glen Turner on Tuesday and were of "the same mindset that led to right-wing American extremists committing the Oklahoma bombing".

State Labor's Luke Foley has launched a stinging attack on the Nationals. Credit:Dean Osland

"For politicians as senior as the Deputy Premier of the state and the federal Agriculture Minister to endorse rage against land-clearing laws is a betrayal of their offices," Mr Foley said.

"Are some of Australia's conservatives now so angry and deranged that they can explain way or 'understand' armed attacks on government employees?