Taieri MP Ingrid Leary said Ms Simmonds had been made "the fall guy" as environmental protection was rolled back by the government.
Dunedin MP and Labour’s environment spokeswoman Rachel Brooking said she supported the regional council’s actions as it got on with protecting Otago’s waterways.
Ms Simmonds reserved comment yesterday.
The regional council voted 7-5 last week to notify its land and water plan by October 31, in advance of a timeline laid out by the Environment Minister.
The council decision was labelled a "disaster" by Federated Farmers, which urged the government to "do more to stop councils continuing to implement freshwater rules" ahead of resource management reforms.
On the other hand, the decision was supported by environmental groups, which said the council had worked hard over the past five years to gather the scientific evidence on which the decision was based.
Nevertheless, because the council disregarded a recommendation from Ms Simmonds to await changes to the plan’s underlying national direction, the council must now outline for her, by May 1, the "costs, benefits and implications" of proceeding with its plan before a new national policy statement for freshwater management (NPSFM) is written.
She then extended the deadline to December 31, 2027.
Ms Simmonds has said the new NPSFM will be reviewed within the next 18 months.
And she has warned the council that notifying its land and water plan before the NPSFM is revised would be a waste of ratepayers’ money.
After a meeting with council leadership in Wellington in February, she said she, along with other ministers, had made the government’s position on the matter "very clear".
Yesterday, Ms Simmonds said she would wait until she received the council’s report on the costs and benefits before commenting further.
The pressure that Ms Simmonds and the government was putting on the council could take environmental protection back decades, Ms Leary said.
"Penny Simmonds is supposed to be a champion for the environment, and a champion for people with disabilities, but in both her portfolios she is becoming the fall guy for bad decision-making by her colleagues" Ms Leary said.
"The council has been put in an impossible position by Penny Simmonds and the National government.
"They’ve told them to wait to update their environmental protections because the government plans to make changes to the requirements — but haven’t given any clarity as to what those changes might be.
"In the meantime our local waterways will suffer."
With the new October 31 notification date in place, regional councillors will receive an updated work programme from council staff in May.
