Federal regulators have long been flummoxed by the growth of the compounding pharmacy industry, which is made up of thousands of small outfits that specially mix medicines for patients, along with an expanding class of industrial-scale manufacturers that ship products to health care providers nationally.

The spotty oversight — veering from lax to tighter scrutiny and slowed by lobbying, aborted legislation, and court decisions — has come into sharper focus since steroid injections traced to the New England Compounding Center in Framingham exposed up to 14,000 patients across the country to fungal meningitis.

So far, the outbreak has killed 25 people and sickened 354 in 19 states, according to the Centers for Disease Control and Prevention.

Former regulators and legal scholars say the Food and Drug Administration has lacked enough authority and resources to effectively monitor compounding pharmacies.

For example, the type of FDA scrutiny used to approve and inspect new drugs — a tightly choreographed process involving multiple clinical trials and inspections of plants where medicines are made according to strict sterility standards — could not easily be replicated for compounding pharmacies. Such pharmacies custom-produce drugs not always available commercially, including treatments that are in short supply or have been pulled from the market because of a lack of demand.

“To perfectly enforce the statutes, the FDA would need a much larger budget,” said I. Glenn Cohen, an assistant professor at Harvard Law School who codirects its Petrie-Flom Center for Health Law Policy, Biotechnology, and Bioethics. “But they’re doing the best they can, given their resources and the political constraints.”

Congressman Edward J. Markey on Monday released a report outlining the roles of state and federal regulators and how the industry “has historically resisted a federal role” in its oversight. A review by his office of pharmacy board records, FDA compliance records, and news reports since 2001 found 23 deaths and 86 serious illnesses linked to products from compounding pharmacies, excluding the latest meningitis cases.

“The risks of allowing the safety of compounding pharmacies to go largely unregulated have been recognized for years, and the devastating tragedies of this outbreak will be felt well beyond that,” Markey said. “The tragedy of NECC is clearly just the tip of an industry iceberg that has long needed reform and federal oversight.”

For much of its history, the FDA has largely ignored compounding pharmacies, leaving their regulation mostly in the hands of state pharmacy boards, which have created a patchwork of rules and standards. But the low-profile business has long worried many in Washington.

The late Senator Edward M. Kennedy sought to bring clarity when he proposed the Safe Drug Compound Act of 2007. But the legislation never came to a vote because of opposition from compounding pharmacy lobbyists and other trade groups that argued such a law would prevent the speedy delivery of medications not available at traditional pharmacies.

“They made sure the legislation wouldn’t see the light of day,” said Sarah Sellers, a pharmacist and drug safety specialist who worked for the FDA on pharmacy compounding issues in 2006. She is now president of Q-Vigilance, a drug-safety consulting firm in Illinois.

The industry’s main trade group, the International Association of Compounding Pharmacies, opposed Kennedy’s bill because it was “too broad and had the potential to disrupt the important and sometimes life-sustaining relationship between compounders and patients,” said David Ball, a spokesman for the organization. He said the group “continues to believe that state boards of pharmacy have the bulk of the responsibility when it comes to state licensure issues.”

Senator Richard Blumenthal, Democrat of Connecticut, wrote to the FDA this month, demanding stricter oversight of compounding pharmacies such as New England Compounding Center. Markey, a Malden Democrat, has asked the Justice Department to launch a criminal investigation of the Framingham company.