Months before the state’s “Amazon tax” law is due to take effect, Colorado’s quest to compel online retailers to collect and pay sales taxes faces renewed opposition — this time from lawmakers on grounds that it would violate consumer privacy.

The controversial law, passed in 2010, stops short of requiring online retailers to collect sales taxes from customers. Instead, it offers them a choice: collect the taxes or be subjected to additional red tape, including a requirement that they file reports identifying their customers and how much they spend on purchases.

But a coalition of online retailers and conservative groups opposed to the law says that provision would violate consumer privacy, effectively allowing the state to collect information on the personal shopping habits of Coloradans without their permission.

Senate Bill 238, sponsored by Senate Majority Leader Chris Holbert, R-Parker, would eliminate the consumer reporting provision before it takes effect July 1, while keeping the rest of the law largely intact. The measure passed the Senate Finance Committee on Tuesday along party lines, but would face an uphill battle if it makes it to the Democrat-controlled House.

“If you go to a bookstore and order a book, (it’s) probably not a big deal,” Holbert said. “But what if you go to a gun website? What if you go to an adult website?” Or, he suggested, what if a transgender person ordered transitional therapy drugs?

“I think that’s ripe for malicious behavior,” Holbert said. “Government has no right to that information.”

Critics have taken to calling it the “tattletale tax” because it would require online retailers to report customers who owe state sales taxes that the retailer didn’t collect on its own. But backers of the law say it is needed to put online retailers on a level playing field with brick-and-mortar businesses. Other states, including Vermont, Louisiana and Oklahoma, have adopted similar laws, using Colorado as a model.

“Making it easier for people who circumvent their local businesses to go online is not what I want to do to our local businesses,” said state Sen. Lois Court, D-Denver, who voted against the bill. “I don’t want to make it easier for people to not go to their brick-and-mortar stores.”

Online commerce has turned the typical Coloradan’s relationship to sales taxes on its head. Under current law, when a customer buys something at a brick-and-mortar store, they’re charged sales taxes on the spot by the retailer. When a customer makes a purchase online — if the store doesn’t collect the taxes — the burden is then on them to pay the tax later on their annual tax return.

And state officials believe that most people don’t pay it. A Colorado Legislative Council fiscal analysis found that in 2015, just 79,000 of the state’s 2.5 million income tax filers paid such taxes, even though as many as eight in 10 people shop online.

If the law takes effect this summer without changes, the fiscal analysis estimates that the state would collect $5.9 million in additional sales taxes. Without the consumer reporting requirement, the state would collect $4.7 million less next fiscal year, the analysis estimated.

“(That’s) not a sum of money the state can afford to lose in a year when we’re pondering significant cuts to schools and other vital services,” said Samantha Curran, a spokeswoman for the Colorado Fiscal Institute, which opposes the bill.

Holbert on Tuesday questioned whether the state would lose that much money. As amended, his bill also would require the state to do more to educate taxpayers of what they owe under existing law.

Online retailers have fought Colorado’s law tooth and nail since it first passed in 2010, saying it would put an unfair burden on out-of-state businesses, requiring them to file reports with the state as well as notify customers by mail that they owe taxes. A series of unsuccessful court challenges delayed the law — and copycat efforts in other states — from taking effect until this summer.

Colorado’s roundabout approach to nudging online retailers to collect sales taxes is largely due to another court ruling that dates back to 1992. In Quill vs. North Dakota, the Supreme Court effectively put the compliance burden on consumers, ruling that taxes are owed but states couldn’t force the companies to collect the money because it was too complicated.

Ironically, Amazon, the company after which Colorado’s law was nicknamed, began collecting sales taxes last year, while other retailers continue to fight its implementation.