Developers and real estate agents in Queens have been using “scare tactics” analogous to the practice of “blockbusting” in the 1960s and ’70s, when real estate agents used race to coerce families in some city neighborhoods to sell their homes and move out, two City Council members of Queens, John Liu and David Weprin, said yesterday.

At a council hearing yesterday on legislation to curb “zonebusting,” Mr. Weprin said predatory brokers and developers coerce homeowners to sell by using impending zoning changes to instill the fear of declining property values.

The legislation, sponsored by 21 council members, would prohibit brokers or developers from advertising that a change in land use or zoning regulations has occurred or will, or that the change many result in a decline in property values, in order to induce a sale or other real estate transactions.

Parts of residential Queens are currently undergoing a down-zoning intended to preserve neighborhood character in areas that are threatened with out-of-scale development. In an attempt to beat the clock, developers are attempting to build the foundations of new buildings before the new zoning regulations take effect.

The bill was inspired by a mass mailing last year to neighborhoods in Eastern Queens. In the letter, a developer, the City Success Corporation of Jamaica, Queens, warned recipients, “The new zoning will prohibit development in your area. If we cannot develop you cannot make a profit on you land. Now is the time to CASH OUT.”

Mr. Weprin, a candidate for council speaker, said the fear caused by that letter and similar mailings reported by council members in Queens and Brooklyn, was enough to coerce a homeowner to sell. Messrs. Weprin and Liu insisted at yesterday’s hearing that down-zoning would not lead to lower property values.

The president of the City Success Corp, Isaac Ivgi, told The New York Sun yesterday that the legislation is unnecessary. He said he had revised the wording of his mailings and had made an agreement with Mr. Weprin to send out 6,000 apology letters. Mr. Ivgi also said his letters were not directed at homeowners, but the owners of vacant lots who stood to benefit from a quick sale before more restrictive regulation takes place.

“People should sell before the zoning changes, and they will make money. Otherwise they will make nothing,” he said.

The president of the Real Estate Board of New York, Steven Spinola, said the legislation would impede brokers from effectively marketing their services and prevent them from providing potential buyers with full disclosure on a property.

“Unsolicited mailings trying to scare people is obviously inappropriate and an unethical way to drum up business. However, brokers are obligated to be truthful and tell people what is happening in a particular property,” he said.

Mr. Spinola said the New York Secretary of State’s office currently maintains oversight of real estate brokers. He said the council’s intrusion was unwarranted. An appraiser, John Cicero of Miller Cicero, said that in general down-zoning would result in lower property values.

“All things being equal, a site that has a lower development potential is going to have a lower value than a parcel with greater development potential,” he said. A violation of the proposed law could result in up to a year in prison and open the way for civil suits.