New legislation before the City Council could make it illegal for New Yorkers to look at a naked neighbor.

Council Member Peter Vallone Jr., a Democrat of Queens, is proposing to outlaw voyeurism by extending a state law that forbids nonconsensual peeping with cameras. He’d apply the law to also include, in the city, peeping with the naked eye.

The law would target offenders who crane their necks to peer under the dresses of women scampering up and down subway stairs. But the legislation also would ensnare anyone caught glancing into the window of a private bedroom or bathroom, which, in a city full of densely packed apartment buildings, is a hazard or a pleasure of urban life, depending on how you look at it, or who your neighbors are.

“If you have an expectation of privacy and someone is looking at you, you would be violating this law,” Mr. Vallone said. It would not, for example, protect someone who stands naked beside her living room window, he said.

The New York Civil Liberties Union said the legislation, which was officially introduced yesterday, was too broad and could lead to abuse. The bill’s “lack of clarity confers a license for abuse on those empowered to enforce the law by leaving it up to the individual police officer to decide which kinds of viewing are lawful and which kinds are degrading and hence unlawful,” the group’s executive director, Donna Lieberman, said in a statement.

Under Mr. Vallone’s bill, characters on the television show “Friends,” which was set in New York City, probably would be serving hard time. The cast regularly watched a man who lived across the street, known as the “ugly naked guy.” A nudist, he might not have pressed charges.

While the bill was designed to deal with repeat offenders who do their peeping in public, Mr. Vallone acknowledged that, “invariably, other situations are going to get caught up in this.”

Violations would be considered misdemeanors, punishable by up to 90 days in jail and a $500 fine.

The bill states that it would be illegal for anyone to deliberately view another person in a private place when they are in a state of undress, having sex, or using the bathroom, without that person’s knowledge or consent. In a public place, it would be illegal for a person to deliberately or repeatedly go to a position to view “another person’s sexual or intimate parts” when “such parts are not otherwise visible to the public.”

A spokesman for Mr. Vallone, Andrew Moesel, said the law would be easier to enforce than some might think. A victim of peeping would be able to call the police and give a description of the offender.

“The most problematic case is going to be people staring into windows,” he said. “It’s like anything else. It won’t be any harder to describe than an assault.”

Mr. Vallone said he crafted the legislation after a number of women in his district complained that a man would routinely stand under the steps of a subway stop and peer up skirts. The police told Mr. Vallone that the man wasn’t breaking the law, he said.

George Crovetto, who repairs and restores old telescopes for Clairmont-Nichols Opticians in Manhattan, said he has never heard of a customer purchasing a telescope to peep into a neighboring apartment.

“We have birders and fisherman and hunters, all type of people buying for looking at the distance, but not to look at people’s apartments,” he said. He added, however, that he’s sure “there will be people crazy in New York, who have nothing better to do than look to see if you are properly dressed through the window.”