(STATE HOUSE NEWS SERVICE) - A top-to-bottom review ordered by Gov. Charlie Baker of the state's maze of regulations continues to generate pushback from a number of outside groups despite the administration's attempts to ease their concerns.

In an effort that the governor has likened to "cleaning the attic," Baker in late March signed an executive order directing state agencies to review the more than 2,000 rules on the books to "relieve the Commonwealth from the burden of unnecessary regulation."

Baker, like Republican and Democratic governors before him, has indicated he's looking to simplify the regulatory code that he says can be an impediment to small business growth and a competitive disadvantage against other states.

However, a group of environmental, legal and liberal-minded business groups continue to worry that the governor's review could be used to roll back some of the state's clean water and air standards, workplace safety codes or restrictions on the use of toxic chemicals.

Thirty-three organizations signed on to letters sent to the Baker administration and the attorney general's office on Tuesday seeking clarity on Baker's directive that regulations "not exceed federal requirements of duplicate local requirements."

That phrase, they said, was not included in a regulatory review undertaken in 1996 by Gov. William Weld that Baker has said he is attempting to mimic through his review.

"That's a small phrase, but it has enormous impact," said George Bachrach, the president of the Environmental League of Massachusetts and the lead signatory on the letter to the administration. "We create our own regulations that are important to us instead of limiting to federal requirements that are often the lowest common denominator."

The administration contends that the groups are overlooking other parts of the directive that would allow for regulations to remain if "less restrictive and intrusive alternatives have been considered and found less desirable based on a sound evaluation of the alternatives."

The executive order also allows Secretary of Administration and Finance Kristen Lepore to grant waivers for those rules deemed "essential for the public health, safety, environment or welfare."

Baker spokeswoman Elizabeth Guyton said in a statement to the News Service that officials in the Office of Administration and Finance have been developing memos to help guide agencies through the regulatory review process.

"The administration values the progress the Commonwealth has made on numerous environmental issues and looks forward to working with stakeholders and the public, as required by statute in the regulatory process, to review regulations that hamper municipal officials' efforts to deliver services and the abilities to live, work and raise a family in Massachusetts," Guyton said.

Senior Baker administration officials, including Undersecretary for Administration and Finance Rachel Madden and the governor's chief of staff Steve Kadish, were unable during a meeting with some of the letter writers earlier this month to quiet their concerns.

Other signees include Ken Kimmell, a former Department of Environmental Protection commissioner under Gov. Deval Patrick, Jack Clarke of Mass. Audubon and Marcy Goldstein-Gelb, of the Massachusetts Coalition for Occupational Safety and Health.

Bachrach, a former Democratic state senator, said, "Federal regulations are often written to accommodate Kentucky and Alabama. I think we believe we're different."

The letter written to Madden does not oppose a regulatory review, but calls on the administration to formally clarify the intent of the executive order, recommending a focus on making sure regulations are "clear, concise and effective for their intended purpose."

Nearly identical language does appear already in Baker's order.

Bachrach, however, said the current structure of the review requires that a lot of faith be put in the administration.

"We have great respect for Governor Baker, but that would be very broad discretion," he said. "We're also concerned that at a time of budget cutbacks and reduced staff, the remaining staff will be distracted by this review of the past rather than looking forward to the future."

A separate letter to Attorney General Maura Healey outlining the same concerns asks the top law enforcement officer to monitor the implementation of the regulatory review process and to "speak on behalf of the protection of our most vulnerable citizens, our civil rights, our public health and our consumer and environmental protection regulations."

A spokeswoman for Healey confirmed her office had received the letter and said the attorney general would review the concerns outlined by the various organizations.

Jesse Mermell, executive director of the Alliance for Business Leadership and the former communications director to Gov. Deval Patrick, said she believes Massachusetts can do better than Washington D.C.

"Part of what makes the Commonwealth an attractive place to do business is that we lead the nation on key fronts like workforce education, healthcare, innovation, and clean energy. It is baffling that we would put the economic growth that comes from being at the head of the class in jeopardy," Mermell said.

The concerns expressed by those who signed the letters are not shared by all with a stake in the state's regulatory scheme.

Chris Geehern, in a recent blog post for the Associated Industries of Massachusetts, said AIM "unequivocally applauds" the Baker administration's benchmarking to federal regulations, citing a "recent fiasco involving state hoisting regulations issued despite a pre-emption in federal law."

"Governor Baker's regulatory reform is a once-in-a-generation opportunity to foster long-term economic growth by taking a clear-eyed look at regulations that are outdated, redundant, ineffective, inefficient or unnecessary," Geehern wrote.