MONTPELIER — Sen. Bernie Sanders is launching a final push to derail legislation in the U.S. Senate that would nullify Vermont’s landmark GMO labeling law and replace it with a national law that opponents say undermines efforts to mandate the labeling of genetically modified foods.

​Sanders distributed a letter Thursday to his Democratic colleagues in the Senate outlining why the legislation crafted by Sen. Debbie Stabenow, D-Mich., and Sen. Pat Roberts, R-Kansas, is insufficient. He is also appealing to the full Senate membership to support an amendment that would replace the Senate bill with Vermont’s law on a national scale.

“The Roberts-Stabenow bill will undermine the strong GMO labeling law that went into effect on July 1st in Vermont. It will also undermine the efforts of other states to label GMOs. The Roberts-Stabenow bill is absolutely unnecessary. As a result of Vermont’s law, many major companies are already labeling their products all over the country. The Roberts-Stabenow bill contains numerous loopholes, and is totally ineffective in terms of addressing the needs of the American people who want to know what is in their food,” Sanders wrote in the letter.

Sanders, in his letter, said the legislation that the Senate will likely vote on Monday has “gaping loopholes” that will allow many GMO foods and ingredients like soybean oil, sugar from GMO sugar beets and high-fructose corn syrup to go unlabeled. The legislation is flawed, Sanders wrote, because it allows food manufacturers to use a digital QR code, or quick response code, rather than clear wording on packaging.

Sanders also faulted the bill for provided an additional two years for the U.S. Department of Agriculture to publish regulations and for not including a mandatory timeline for compliance or federal penalties for not complying with the law.

“Ultimately, this compromise is no compromise at all if the federal government will simply override states’ laws on GMO labeling without a meaningful federal standard to replace them,” Sanders wrote. “I urge you to oppose the current Roberts-Stabenow language, and instead support my comprehensive national labeling amendment, which would provide what nearly 9 out of 10 consumers want.”

Sanders’ amendment would make Vermont’s GMO labeling law the federal law. It faces long odds, however, after the Senate voted Wednesday to advance the Roberts-Stabenow bill on a procedural vote with a tally of 65 to 32.