Several states, led by Tasmania, are pushing back against the federal government's proposed national gun buyback saying the plan lacks detail and could cost them millions.

Tasmania's Police Minister says any buyback should be fully funded by Canberra warning it could cost Tasmanians around twenty million dollars - and impact legitimate gun owners.

He says his state does back tougher measures to keep firearms out of the wrong hands but that all reforms should be properly funded and with proper consultation with the states.