Washington - Cheerleaders are a staple of American professional sports.

But the treatment of the scantily-clad women who encourage their teams from the sidelines is drawing scrutiny.

The New York Times published an article on Wednesday about questionable treatment of cheerleaders for the Washington Redskins, a National Football League (NFL) team, during a trip by the squad to Costa Rica in 2013.

And cheerleaders for two other NFL teams, the New Orleans Saints and the Miami Dolphins, have filed lawsuits recently alleging discrimination.

The Times spoke to several members of the 36-strong Redskins cheerleading squad who went on the weeklong trip to an exclusive resort in Costa Rica for a photo calendar shoot.

Speaking anonymously, several cheerleaders said they were made to be pose topless or wearing only body paint for pictures taken for the calendar - although it would not include nude shots.

They complained that sponsors and luxury suite holders at Redskins stadium - all of whom were men - were granted access to the photo shoots.

Nine cheerleaders were also allegedly made, at the end of a 14-hour day of posing and dance practice, to attend an event at a nightclub as escorts for the sponsors.

"They weren't putting a gun to our heads, but it was mandatory for us to go," one of the cheerleaders told the Times. "We weren't asked, we were told."

The arrangement did not involve sex, the cheerleaders said, but they were not comfortable with it.

Stephanie Jojokian, the director and choreographer of the Redskins cheerleading squad, insisted she had not forced anyone to attend the nightclub event.

"I was not forcing anyone to go at all," Jojokian told the Times. "I'm the mama bear, and I really look out for everybody, not just the cheerleaders.

"It's a big family. We respect each other and our craft," she said. "It's such a supportive environment for these ladies."

The newspaper said the cheerleaders were not paid for their participation in the Costa Rica trip but received transportation costs, meals and lodging.

The Times said it had interviewed dozens of current and former cheerleaders for its story.

"They enjoyed performing at games, developing friendships with other cheerleaders and participating in charity work," the Times said. "But they were disturbed by some of the extracurricular requirements that put them in what they considered unsafe situations."

The Redskins issued a statement saying the cheerleader squad "is one of the NFL's premier teams in participation, professionalism, and community service.

"Each Redskin cheerleader is contractually protected to ensure a safe and constructive environment."

Former Saints cheerleader Bailey Davis filed a complaint in March with the Equal Employment Opportunity Commission after she was fired by the team.

She alleges that the Saints impose double standards in their treatment of male players and cheerleaders.

Dolphins cheerleader Kristan Ware lodged a complaint with the Florida Commission on Human Relations last month alleging discrimination because of her gender and her Christian faith.

She claimed that leaders of the cheerleading squad told her to stop publicly discussing her virginity.