The battle between landlord and tenant groups is heating up in New York City.

An organization that represents landlords, the Rent Stabilization Association, filed a lawsuit in state Supreme Court last week challenging the legal underpinnings of the Tenant Protection Act, a four-month-old law that was championed by the City Council speaker, Christine Quinn.

According to the suit, inclusion of the term “harassment” as a technical violation within the law is illegal.

The general counsel for the Rent Stabilization Association, Mitchell Posilkin, said there is no way for a city inspector — or anyone for that matter — to objectively evaluate whether “harassment” has taken place.

In response, Ms. Quinn and Council Member Melissa Mark Viverito organized a rally at City Hall in support of the law.

The lawsuit is the latest in a long-running landlord-tenant tussle, and comes amid a push by the City Council to wrest more control of the Rent Guidelines Board, which oversees the city’s rent-stabilized apartments.

Ms. Quinn is backing a bill in the state Legislature that would require council approval of board members, deny rent increases for one year for any apartment with serious violations, and require the use of a landlord’s income and expense information in determining whether a rent increase is warranted.

In addition, the state’s Division of Housing and Community Renewal is currently reconsidering a provision within the law that allows landlords to deregulate apartments and evict tenants by promising to demolish the building.

In an interview yesterday, Mr. Posilkin said it was simple for an inspector to determine whether there is heat or hot water, or if lights in the hallway are working, but impossible to determine harassment.

“For the first time, they are making a violation something that is not objective but something that is subjective. All we are saying is that this is not the purpose of the housing code,” Mr. Posilkin said. “What the council has done is ask inspectors to look into the mind of a landlord.”

Ms. Quinn issued a statement yesterday: “This attempt to overturn the Tenant Protection Act speaks to the absolute necessity of having this law on the books. Obviously, some landlords feel they need to protect a pattern of behavior designed for only one purpose — to get people out of their homes…. Instead of forcing us to waste taxpayer money in court, landlords should use their resources to ensure full compliance with the law.”