U.S. Rep. Marsha Blackburn believes a law that critics say provided less scrutiny of drug companies and distributors had unintended consequences and should be "addressed immediately," a spokesman said Monday.

The comment comes in light of a joint investigation by "60 Minutes" and The Washington Post in which a whistleblower accused Blackburn and other congressional lawmakers of passing the law that led to lax scrutiny and a rise in opioid deaths.

The story, published Sunday, featured an interview with Joe Rannazzisi, who previously ran the U.S. Drug Enforcement Administration's Office of Diversion Control. The report also comes as Blackburn has launched a bid for the Senate seat held by U.S. Sen. Bob Corker.

Rannazzisi, along with Jonathan Novak, a former DEA attorney, pointed to a bill sponsored by Rep. Tom Marino (R-Pa.) and co-sponsored by 14 others, including Blackburn, which they said stripped the federal agency of the ability to freeze suspicious shipments of opioids.

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Prior to the legislation's passage in 2016, the DEA had been able to halt drug distributors from sending millions of opioids to doctors and pharmacies who law enforcement thought were feeding people addicted to opioids.

The sponsors of the bill previously said it was necessary in order to ensure patients had access to pain medicine.

In a statement to the USA TODAY NETWORK - Tennessee on Monday, a spokesman for Blackburn, who launched her Senate campaign Oct. 4, said the congressman had a long history of fighting the opioid epidemic.

"If there are any unintended consequences from this bipartisan legislation — which was passed unanimously by the House, Senate and was signed into law by President Obama — they should be addressed immediately," the spokesman said.

Earlier in the day, U.S. Sen. Claire McCaskill, D-Mo., said she will push new legislation to undo the 2016 measure.

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Also on Monday, Sen. Joe Manchin, D-W.Va., called for President Donald Trump to withdraw his nomination of Marino to serve as the lead of the Office of National Drug Control Policy, which requires Senate confirmation.

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In addition to co-sponsoring the legislation, Blackburn received $120,000 in campaign contributions from the pharmaceutical industry, according to The Washington Post.

The Washington Post and "60 Minutes" investigation also noted that Blackburn and Marino wrote a 2014 letter in which they accused Rannazzisi of trying to "intimidate the United States Congress" while asking for an Inspector General's probe into Rannazzisi.

Back home, critics are blasting Blackburn over the bill.

Former U.S. Rep. Stephen Fincher, who is considering entering the Republican Senate primary, said the overall issue is illustrative of how out-of-touch politicians in Washington, D.C., have been.

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"This goes right to the heart of why we are probably going to get into the race," he said. "This is an issue that shows Tennesseans ... want someone to stand up against special interests."

Without mentioning Blackburn by name, Fincher questioned the value of "career politicians," saying the findings of the "60 Minutes" and Washington Post report "makes you really have to question who is best to go up there and represent this great state that we have."

Fincher, who was in Congress at the time, was among the House members who unanimously approved the legislation without objection.

Aside from Fincher, Democrats quickly criticized Blackburn for her involvement in the legislation.

“At the crucial time when she should have been protecting us, Rep. Blackburn championed a bill that imprisoned even more Tennesseans in a devastating cycle of drug dependence," said Mary Mancini, chair of the Tennessee Democratic Party, citing statistics on the number of overdose deaths in Tennessee in recent years.

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Overdose deaths continue to rise in Tennessee, fueled in large part by both prescription and illicit opioids. In 2016, at least 1,631 died from overdoses in the state — a number that experts say is an undercount of the real toll.

"As a public servant, Blackburn's job is to protect Tennesseans from harm," Mancini said. "She's supposed to have our backs. Instead, she has sacrificed the most vulnerable of us for what she could get from powerful special interests.”

In a statement, James Mackler, an Iraq War veteran and Nashville attorney who is seeking the Democratic nomination for the U.S. Senate seat held by Corker, vowed to stand up to special interests and lobbyists. Corker announced late last month that he would not seek re-election.

"That Congresswoman Blackburn would champion legislation like this while Tennesseans face an opioid epidemic is all one needs to know about her priorities," Mackler said.

Last month, Tennessee Attorney General Herbert Slatery issued subpoenas and demand letters to pharmaceutical companies and distributors as part of a 41-state coalition’s investigation into “unlawful practices in the marketing, sale, and distribution of opioids.”

Distributors AmerisourceBergen, Cardinal Health and McKesson were among those served with demand letters — all three companies were named in the "60 Minutes"/Washington Post investigation.

Anita Wadhwani contributed to this report. Reach Joel Ebert at jebert@tennessean.com or 615-772-1681 and on Twitter @joelebert29.