SPRINGFIELD — State Sen. Bill Brady has retreated from a controversial plan he proposed involving animal euthanasia after facing heavy pressure from the Humane Society of the United States.

Brady of Bloomington proposed allowing veterinarians to use carbon monoxide chambers to euthanize more than one cat or dog at a time.

Last year, state lawmakers changed laws to require that if a pet is going to be euthanized in such a chamber, it must be done one at a time.

Brady said a veterinarian in his district asked that lawmakers consider making the change. But Wednesday, Brady moved to shelve the legislation.

Brady, the possible GOP candidate for governor, said he wanted to have a debate over how to tweak the plan but pointed criticisms from the Humane Society have killed that possibility.

“It’s not ready,” Brady said of the legislation. “And the political games were distracting from the discussion.”

Jordan Matyas, Illinois director for the national Humane Society, said the organization criticized Brady because using carbon monoxide to kill multiple cats or dogs at once could cause unnecessary agony for the animals.

He argued they wouldn’t die quickly.

“This is going to take at least a couple of minutes,” Matyas said.

Matyas said the euthanasia method pushed by Brady is “extremely rare,” as most veterinarians use injections.

“This is basically the ancient form of doing it,” Matyas said.

Brady filed his plan in the General Assembly but moved to change it Wednesday. He said he won’t be trying to push the legislation forward.

The legislation is Senate Bill 2999.