Ikaroa-Rawhiti MP and local government spokesperson Meka Whaitiri said the Maori Party claims that they were still negotiating were disingenuous.
"To say they'll win further concessions at the committee stage is a cop-out and misleading.
"They made this deal with National back in November; if they haven't negotiated the removal of the s360D powers by now, they never will.
"This bill introduces sweeping new powers to knock out GM rules in local plans and the Māori Party's support is a blow to our local councils and regional economies."
Tukituki Labour candidate Anna Lorck said it was important that the region worked together to fight for local democracy and protect the area's right to be GM-free.
"Labour's policy is clear, Labour is here for Hawke's Bay, we are united and are working together. We understand how important the GM-free marketing opportunity is for Hawke's Bay's exporters and the regional economy.
"Unlike National that is doing everything it can to strip Hawke's Bay's local powers away and undermining our right to make key decisions."
Tukituki National candidate Lawrence Yule said he maintained his support for Hawke's Bay as a GM-free growing region.
"I have had this position for a long time and the Government is aware of that.
"I have spoken to the Prime Minister and others and told them that if I happened to win the election I would espouse to my fellow colleagues that that's the position I support."
Ms Lorck, however, welcomed Mr Yule to work with the region right now.
"This is crunch time for Hawke's Bay and we need decisive action now, today, it's what he does right now that matters."
Meanwhile, Tukituki MP Craig Foss said Environment Minister Nick Smith was less concerned about the Hastings District Council's GM-free declaration than he was about Auckland's ban on genetically modified organisms in its unitary plan that could prevent a liver cancer trial in that region.
"There are different views and understanding of this issue across Hawke's Bay.
"I am very respectful, and personally know many of the growers of our stunning produce and have discussed their proposals with Minister Smith.
"Negotiations with our support parties are continuing in good faith."
Having passed its second reading the bill now goes to the committee of the whole house, which all MPs belong to, and each part will be considered and debated in detail.
Members can propose amendments to the bill, and once the final text is agreed on the bill is re-printed and ready for its third reading.