The city is considering whether to appeal a federal judge’s decision to force the New York Police Department to disclose secret documents about its undercover surveillance of political groups before the Republican National Convention in 2004.

The decision by the federal magistrate judge, James Francis IV, would allow New York Civil Liberties Union lawyers to see hundreds of documents about the NYPD intelligence program that the police department has sought to protect.

The civil liberties group is suing the city on behalf of a group of the estimated 1,800 people arrested while protesting at the convention following a sweeping police surveillance program that had involved sending undercover investigators to monitor activists in other cities and countries.

The NYCLU hailed the decision as a victory yesterday.

The set of documents Judge Francis has ordered the police department to disclose include raw intelligence data, such as field intelligence reports prepared by undercover officers. Police would also have to share police commentary in e-mailed and handwritten communications about activist email correspondence they were monitoring.

The NYPD’s deputy commissioner of intelligence, David Cohen, has testified that some of the documents sought by the plaintiffs, including the field intelligence reports, would make it possible to identify undercover officers and would disclose the “methods used by the NYPD in an undercover investigation,” according to court papers.

The judge disagreed. “The very limited information being produced to the plaintiffs reveals nothing about police investigatory tactics beyond that fact that undercover officers or informants attended meetings of, and protests organized by, various activist organizations,” Judge Francis wrote in his decision. “This is hardly a revelation.”

The judge did agree to some of the redactions requested by the police department, however. In order to protect its agents and methods, the names, e-mail addresses, and other personal information about individual undercover officers could be concealed, he ruled.

Only the lawyers for the plaintiffs would be able to see the intelligence documents.

The police department has already given out more than 600 documents, including summaries of the raw reports, to comply with a ruling by Judge Francis in May — a decision the city decided not to appeal.

At that time, the judge indicated that he would probably order the department to release the raw intelligence documents, too, but took the last few months to review the documents himself.

A lawyer for the city, Peter Farrell, said the city was reviewing the judge’s decision to determine if it would appeal. Police department officials reserved comment until they have reviewed the court papers.