Olympic gold medalist Caitlyn Jenner has said she supports a local New York official’s order banning female sports teams with transgender athletes from using county-owned facilities.

The ban applies to more than 100 athletic facilities in New York City’s Long Island suburbs.

Speaking alongside Nassau County executive Bruce Blakeman, Jenner said allowing transgender athletes like herself to compete against other women will “ruin women’s sports” for years to come.

“Let’s stop it now while we can,” said the reality television star, who came out as a transgender woman in 2015.

The LGBT Network, a Long Island-based advocacy group, called Jenner’s comments a “baffling contradiction” to her own identity as a transgender woman that is “not only hypocritical but also harmful” to the LGBTQ community.

“It is disheartening to witness someone who has experienced the challenges of being marginalised actively contribute to the oppression of others within the same community,” David Kilmnick, the group’s president, said in a statement.

“Such actions only serve to amplify the voices of intolerance and detract from the collective efforts towards a more inclusive society.”

Mr Blakeman, a Republican elected in 2022, issued an executive order in February requiring any teams, leagues or organisations seeking a permit from the county’s parks and recreation department to “expressly designate” whether they are for male, female or co-ed athletes.

Any teams designated as “female” would be denied permits if they allow transgender athletes to participate.

The ban does not apply to men’s teams with transgender athletes. It covers all Nassau County-owned facilities including ballfields, basketball and tennis courts, swimming pools and ice rinks.

Jenner, 74, competed against men when she won the Olympic gold medal in the decathlon in 1976. She said she has “sympathy” for LGBTQ people and “understands their struggles” but argued that allowing transgender people to compete with women would undermine gains female athletes achieved under Title IX, a law banning sex discrimination in programmes that receive federal funds.

“All I’m trying to do is protect women,” Jenner said on Monday.

Jenner, a supporter of former president Donald Trump, has been a vocal opponent of transgender athletes competing in women’s sports. She has long lived in the Los Angeles area and ran unsuccessfully for California governor as a Republican in 2021.

Mr Blakeman has argued the ban is intended to both foster fair play and protect girls and women from getting injured if they play against transgender women. His executive order, however, also covers sports including swimming, gymnastics, figure skating and track events, where there is no physical contact between competitors.

The executive order also takes decisions about who can play out of the hands of leagues and gives it to the government.

The Long Island Roller Rebels, a local women’s roller derby league, asked a New York court to invalidate the county order, saying it violates the state’s anti-discrimination laws.

The New York Civil Liberties Union, which filed the lawsuit on behalf of the league, called Jenner’s appearance “another disgraceful attempt” to target and villainise transgender women and girls.

Attorney general Letitia James, a Democrat, said Mr Blakeman’s order is “transphobic and discriminatory” and violates state law.

Mr Blakeman has filed his own lawsuit asking a federal court in New York to affirm that the order was legal.

The order is part of a growing number of anti-transgender athletic restrictions imposed nationwide. Bills banning trans youth from participating in sports have passed in some 24 states, though some have been blocked by ongoing litigation.