A Philadelphia judge yesterday ordered prosecutors to disclose the identities of two police undercover officers involved in an altercation last year with antiracism activists who thought the officers were skinheads attending a Ku Klux Klan rally.

Municipal Court Judge Marsha H. Neifield said she was concerned with the safety of undercover police officers in the scuffle at Center City's Love Park. But the judge said she was also offended that police did not even anonymously mention the presence of the two officers in reports filed after four antiracism activists were arrested.

Without that information, which she said was mandatory to disclose, it was impossible for defense attorneys to argue that the officers - and not the activists - precipitated the July 23, 2007, altercation.

The judge set another hearing for Jan. 26 to give the District Attorney's Office time to decide whether to appeal the order to Common Pleas Court.

The four antiracism activists - Jared Schultz, 29, and Thomas Keenan, 23, both of Frankford; Jason Robbins, 29, of West Philadelphia; and James McGovern Jr., 59, of Paulsboro - were arrested after they followed the officers, whom they believed were neo-Nazi skinheads, to a waiting SUV, kicked at the vehicle's sides and broke a rear window.

The vehicle was an unmarked car belonging to the FBI's Philadelphia antiterrorism task force. The car was taken to the rally by agent Stephen Powell and Philadelphia detective Lt. Sean Brennan, who said they went to the KKK rally - which never happened - for surveillance purposes.

McGovern pleaded no contest to charges of criminal mischief, conspiracy and harassment and was sentenced by Neifield to three years probation, anger management therapy and $600 restitution.

The other three maintained they were innocent. After learning the two undercover officers' presence was missing from all police paperwork, defense attorneys Paul J. Hetznecker and Lawrence S. Krasner argued that they needed to question the officers to see if they "set up" the activists.

The lone defense witness, law student Sheila Maddali, who was present on July 23, 2007, said antiracism groups showed up at Love Park a half-hour before the noontime Klan rally.

No KKK members ever showed, but the witnesses said the two undercover officers walked into the park dressed like skinheads.

One activist asked if the two were Klan members and Maddali said one replied, "So what if we are?"

She said others began heckling the officers, calling them fascists and asking, "So you like to lynch black people?"

"We can lynch whoever we want," was the officer's reply, Maddali said.

Krasner and Hetznecker argued that the Klan rally itself seemed suspicious. Both police and FBI witnesses said they learned of the purported rally through a leaflet and through a demonstration permit filed with city officials. But they also said the leaflet no longer exists, and city officials said the Klan never applied for or received a permit.

Powell testified that he did not know the undercover officers were there until he and Brennan parked near Love Park. Powell said he recognized the two officers from previous assignments, spoke to one of them and was told, "These guys want to fight us."

Three law-enforcement witnesses called to testify by Assistant District Attorney John O'Neill, including Powell and Brennan, refused to identify the two undercover officers, and O'Neill argued their names must be kept secret to protect their well-being.