In a showdown over Internet privacy, the newly conservative Federal Communications Commission and the Republican-led Congress are trying to block tough Obama administration rules that limit how broadband Internet providers use their customers’ personal information.

At stake is the way Internet service providers (ISPs) such as Comcast Corp., AT&T Inc., and Verizon Communications Inc. use and store the sensitive data they collect, including customers’ locations, their financial information, Social Security numbers, and Internet browsing habits.

“Your ISP knows every click you make online, and the ISPs can use their unique position as broadband gatekeepers to collect and use sensitive information about subscribers,’’ said US Senator Ed Markey, a Massachusetts Democrat and a strong supporter of the Obama-era privacy standards, who is working with liberal Internet activists and privacy advocates to defend them in Congress.

Broadband companies want to use this customer information to sell personalized online advertising, like the ads that generate billions of dollars for online businesses such as Facebook and Google. But in October, the FCC adopted rules that would require broadband companies to get users’ explicit permission before collecting a range of sensitive data, such as where they go on the Internet and what apps they use.

The companies say the new rules put them at a disadvantage, versus giant online advertisers, which are governed by a less stringent set of standards issued by the Federal Trade Commission. For example, Google doesn’t need to ask permission to track customers’ browsing habits.

The industry’s main trade group, the Internet & Television Association, said in a statement that the FCC policy “would create an inconsistent and confusing patchwork that will confuse consumers and weaken data protection online.’’

The new Republican FCC chairman, Ajit Pai, agrees, and on Friday said he plans to block some of the rules from taking effect as scheduled on March 2.

“All actors in the online space should be subject to the same rules, and the federal government shouldn’t favor one set of companies over another,’’ Pai said through an FCC spokesman.

His action will delay implementation of a rule beefing up data security standards for personal information stored by broadband companies. Other portions of the rules are scheduled to take effect by December, but Pai has not indicated whether he will take steps to block those provisions, as well.

Markey denounced Pai’s maneuver, saying in a statement that it “could make subscribers’ sensitive information . . . more vulnerable to breaches and unauthorized use.’’

Meanwhile, Republican Senator Jeff Flake of Arizona is planning a more aggressive attack on the rules.

He plans to introduce a resolution to override the FCC using the Congressional Review Act, a law that lets Congress cancel rules issued by federal regulatory agencies, by a simple majority vote. The CRA, enacted in 1996 as part of then-House Speaker Newt Gingrich’s “Contract with America,’’ has rarely been used.

But since President Trump’s election, and with the GOP controlling both houses of Congress, the CRA has come to be seen as an efficient way to quickly eliminate many regulations issued during the Obama administration.

The CRA approach is particularly radical, because if the law is used to kill a regulation, the agency is permanently barred from issuing similar regulations without congressional approval. If it’s used on the FCC rules, the agency would no longer be able to establish any privacy standards for broadband companies, unless Congress explicitly authorized it.

Neema Singh Guliani, legislative counsel for the American Civil Liberties Union, said this would leave consumers defenseless against privacy violations by broadband providers. Guliani said that when the FCC in 2015 decided to regulate Internet companies under the same law that covers phone companies, it removed those companies from FTC jurisdiction. So if Congress repeals the regulation, Guliani said, ISPs would be in a kind of regulatory twilight zone, not bound by privacy rules of the FCC or the FTC.

Markey is teaming up with the ACLU, as well as Consumers Union, the publisher of Consumer Reports magazine, and the Internet activist groups Free Press and Public Knowledge for a Monday teleconference to urge Congress to leave the FCC rules alone. But given the Democrats’ minority status, Markey will need bipartisan backing to prevail.

Hiawatha Bray can be reached at hiawatha.bray@globe.com. Follow him on Twitter @GlobeTechLab.