The National Party could face an embarrassing defeat on its major planning reforms unless it agrees to drop changes that affect genetically modified organisms.
The Maori Party, whose vote is needed to pass the reforms, opposes a change to the Resource Management Act (RMA) that will prevent councils from banning GE trials or releases in their regions.
The clause allows the Government to overrule councils not only on GMOs but on other activities related to the RMA.
Environment Minister Nick Smith refused to comment today, saying he wanted to "have discussions directly with the Maori Party".
But he has previously defended the provisions opposed by the Maori Party, saying councils could prevent important medical and scientific advances if they introduced GE-free policies.