An Arizona lawmaker who helped pass one of the nation's toughest DUI laws is now pushing for changes that critics say would defang it and put lives at risk.

The bill introduced by Republican state Sen. Linda Gray would cut from one year to six months the amount of time a DUI interlock device must be used by first-time offenders in Arizona. The interlock device -- basically, a breathalyzer attached to the starter of a vehicle -- prevents motorists with a blood alcohol level higher than .08 percent, from turning on their engine.

Gray, who has championed tougher DUI laws for the past 13 years, says six months is a long enough punishment. At the same time, she says her bill strengthens the law by adding other restrictions.

But Mothers Against Drunk Drivers (MADD) and interlock companies fervently oppose Gray's bill.

"We don't understand why we want to take a law that is working for our state and change it," Kelly Larkin, executive director of MADD, told FoxNews.com.

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Larkin said since the inception of the law in 2007, DUI fatalities have plunged in Arizona by 46 percent while it has fallen by 20 percent in the rest of the country.

"Arizona has the strongest interlock law on the books," she said. "If we start lowering our standards, what are the states around us going to think? We want them to be as safe as we are."

Jay Lopez, the owner of Ignition Interlock of Arizona, said the state should be focused on strengthening the law rather than weakening it by reducing the interlock requirement.

"If it's not broke, why try to fix it?" he said. "We should be focusing on the problems we have right now with compliance."

According to Gray, only about 30 percent of first-time offenders have met the requirements to get the interlock and complete the program. The law currently prevents those out of compliance from renewing their driver's license. Her bill prevents first-time offenders who don't comply with the penalties from renewing their vehicle registration as well.

"That's how we'll try to increase compliance," she said.

Rep. David Burnell Smith, a lawyer who defends DUI victims and whose own legislation would eliminate the requirement for first-time offenders, said other reasons can explain why the number of DUI fatalities has tumbled.

"More aggressive law enforcement, more emphasis on not drinking and driving," he said. "I don't think the interlock device has done that in and of itself."

Smith's bill is stuck in committee. He said he will support Gray's bill if his doesn't get passed.

"It benefits everyone except interlock companies if we remove the requirement of the interlock for first-time offenders, giving them more money to pay fines, jail cost and pay for alcohol education," he told FoxNews.com. "Alcohol education is more important than interlock."

Larkin said the financial burden on first-time offenders isn't that great. It costs about $90 to have it installed in a car and $50 a month on average to maintain it.

Lopez agreed that the interlock is not financially burdensome for first-time offenders, calling that reason for opposing the bill a "cop out."

"The interlock program averages $70 to $80 a month -- that comes out to $2 bucks a day," he said. "When people drink, they spend more than $2 a day. If you have money to go out and drink every weekend and party, you have money for the interlock."

Lopez said if affordability is such a concern, an indigent program should be created that interlock companies fund.

"But that's not the issue," he said. "It's not that people can't pay. It's that people are still drinking and driving."

Lopez said the new bill would give offenders more incentive to avoid the program. But while acknowledging that the law has been a financial boon to interlock companies, he said the new bill wouldn't eat into their profits because they can always raise their rates and the law has reduced the number of fatalities.

"Which one do you prefer?" he said. "I drive in Arizona too. My kids drive here too. It's a big concern."

Different versions of the ignition-interlock law exists in 48 states and 12 require the device for first-time offenders, according to the National Conference of State Legislatures. The length of time first-time offenders must use the devices varies, from 30 days in Oklahoma to six months in Oregon, New Jersey and Missouri and one year in New Mexico and Pennsylvania.

Gray's legislation has cleared the Senate and is now being considered by the House. She said she takes exception with the notion that she would introduce a bill that would weaken the law when she has been advocating for tougher DUI laws since 1997 -- after two Phoenix cops were killed by drunken drivers within a few months of each other.

"Nobody has brought more legislation concerning drunk drivers. That's why we have a decrease in the number of DUI fatalities," she said. "I've worked very hard on trying to make sure this tragedy of somebody driving a loaded weapon doesn't happen. So to say I'm lessening it, I'm giving those people a chance to turn their life around."