Richard Trumka, the head of America’s biggest labor organization, opened its October national convention in an unusual way: the AFL-CIO president read a passage from the code-of-conduct and gave out the contact information of two people designated to field any complaints about sexual harassment or other discriminatory or inappropriate behavior.

“It’s a zero-tolerance policy,’’ Trumka told reporters that day. “We think we’re on the cutting edge of that. And if we aren’t, we want to be there.’’

Less senior activists say the country’s biggest union federation — and the broader labor movement — still have a ways to go. The AFL-CIO’s chief budget officer and assistant to Trumka, Terry Stapleton, resigned Monday following allegations of sexual harassment. The Service Employees International Union, the second-biggest union in the United States, is reeling from its own harassment scandal that has seen the departure of four senior staff.

It is a high-stakes reckoning for the weakened labor movement, which champions workplace dignity and the power of unions to protect against exploitation and harassment. Dozens of current and former movement employees say the groups’ leaders too often fail to protect their own staff from abuse or to take sufficient action in response, creating toxic cultures that have turned off promising young organizers.

“Sexual harassment is a reason women organize,’’ said Kate Bronfenbrenner, a former organizer and now a lecturer at Cornell University’s labor relations school. “But it can be a reason women don’t organize.’’

“The recent news regarding sexual harassment in numerous industries has shown that no organization, including our own, is immune to a culture that has allowed both women and men to feel unsafe and threatened on the job,’’ the AFL-CIO said in a joint statement from Trumka, secretary treasurer Liz Shuler, and executive vice president Tefere Gebre. “As the premier organization for working people, we recognize that we bear a special responsibility to lead by our actions and example.’’

Some characteristics of union organizing may make it easier for bad actors to get away with abuse, said Rutgers professor and former organizer Janice Fine. Macho norms still prevail in many unions. Staff work long hours doing emotionally draining work, often far from home. Organizers are loyal to the workers the union represents and loathe to do anything that could be perceived as damaging to a campaign.

“There’s still this idea that in order to do it, you have to work 24 hours a day, you have to be willing to move, you have to put work above all other things,’’ said Fine. That’s included trying to overcome sexism by excelling at work rather than by confronting it directly. Recently, she said, that’s begun to change.

Scott Courtney, an executive vice president at SEIU and a key architect of the high-profile “Fight for 15’’ campaign, resigned in October amid an investigation into alleged “sexual misconduct and abusive behavior.’’ During a career that spanned decades, people who worked for Courtney say he was known for dating his subordinates. Women warned each other and raised concerns about his behavior with higher-ups over the years, former employees said. Seventeen years ago, dozens of employees presented their concerns about Courtney in writing to national leaders, according to people who participated.

Courtney did not respond to a request for comment. An SEIU spokeswoman declined to comment on specific personnel matters because the internal investigation is ongoing.

That investigation also led the union to terminate two members of the senior staff, SEIU said. Another top Fight For 15 leader, Kendall Fells, resigned on Nov. 2. Without commenting individually on the departures, the union said that day that the investigation had “brought to light the serious problems related to abusive behavior towards staff, predominantly female staff.’’ Fells declined to comment.

“We are incredibly grateful to the people who have come forward,’’ said SEIU executive vice president Leslie Frane, who described the organization’s response as swift and decisive. “Our mission is about making sure that working people are treated with respect and dignity, have good wages and a voice on the job. We are committed to making sure that the work environment for our staff lives up to those values.’’