Farmers say they can be trusted not to return to the dark old days of broadscale tree clearing when laws are relaxed in Queensland.

Opponents say Premier Campbell Newman has broken an election promise and have labelled him the state's biggest threat to biodiversity.

His government planned to pass controversial amendments to the Vegetation Management Act on Tuesday.

Cattle, starving from prolonged drought, will be allowed to graze in five national parks and eight reserves until the end of 2013, and beyond that date if needed.

Farmers will also be able to clear their land without permits for routine management, such as building fences.