CONCORD, N.H. — Governor Kelly A. Ayotte vetoed legislation on Tuesday that would have rolled back anti-discrimination protections for transgender people in bathrooms, locker rooms, detention facilities, and sports.

In so doing, Ayotte followed in the footsteps of her predecessor, Chris Sununu, a fellow Republican and close ally, who had vetoed the same legislation last year.

While proponents said House Bill 148 would protect people’s privacy rights and physical safety, opponents said the measure would allow discrimination against transgender people.

Ayotte said she sees “legitimate privacy and safety concerns” on this topic, but believes HB 148 was too broad and impractical, and risked creating “an exclusionary environment” for some community members.

“While I believe that the legislature should address this serious issue,” she said, “it must be done in a thoughtful and narrow way that protects the privacy, safety, and rights of all New Hampshire citizens.”

The legislation would have allowed public and private organizations to bar transgender individuals from using certain facilities and participating in certain activities that align with their gender identity.

Unlike the bathroom bills that have passed in other states, such as Florida and Utah, the legislation in New Hampshire would have allowed for sex-based separation in certain settings, without requiring it.

Every state in New England has adopted legal protections on the basis of gender identity. Had this bill been signed into law, New Hampshire would have become the only state in the region to add exceptions for transgender people in certain circumstances, according to Movement Advancement Project.

The legislation would have curtailed protections that Sununu signed into law, when legislators added gender identity to New Hampshire’s existing nondiscrimination statute.

When he vetoed a bill like HB 148 last year, Sununu reiterated his prior statement that discrimination “is unacceptable and runs contrary to New Hampshire’s Live Free or Die Spirit.” He said the bill sought to solve problems that hadn’t cropped up in New Hampshire, and would invite “unnecessary discord.”

Republican Representative Jim Kofalt of Wilton, the prime sponsor of HB 148, disagreed with Sununu’s assessment and said school districts in New Hampshire have struggled to regulate bathroom usage under the current law.

“This is an important change that we need to make in our law so that we can respect everyone’s privacy and security,” he told senators in May.

The American Civil Liberties Union of New Hampshire opposed the bill, which policy advocate Courtney Reed called “egregiously cruel legislation” that would permit discrimination.

“This discriminatory, detrimental, and regressive bill is an attempt to expel transgender Granite Staters from public life,” she said in a statement ahead of the bill’s passage.

Ayotte said in her veto message that she worried HB 148 would “spur a plethora of litigation against local communities and businesses.”

Ayotte said the provisions of HB 148 that pertain to athletics for women and girls are “weaker” than New Hampshire’s current law, which is being challenged in federal court.

Legal challenges to bathroom bans have had mixed results elsewhere. Some bans have been upheld, such as a March decision from an appeals court in Idaho, while some efforts to reinstate bans have been rejected.

Amanda Gokee can be reached at amanda.gokee@globe.com. Follow her @amanda_gokee. Steven Porter can be reached at steven.porter@globe.com. Follow him @reporterporter.