Nielsen Media Research announced Wednesday it is delaying the launch of Local People Meter Service in Washington and Philadelphia from Thursday to June 30 “at the request of many clients and the Media Rating Council.”

The move comes a day after it became known that 16 TV station groups and CBS asked Nielsen to halt the rollout of the controversial LPM service until Nielsen wins full accreditation for the service in each of the markets in which it is already deployed.

So far, Boston and San Francisco are the only two LPM markets that have been fully accredited by the Media Rating Council, the congressionally mandated watchdog agency for the media research industry. New York, Los Angeles and Chicago have received only conditional accreditation from the MRC.

In announcing the delay, Nielsen said the extension “will allow for the comparison of demographic data from the May measurement period. It is apparent that many of our clients in these markets require more time to understand the impact that this change in methodology will have on their businesses.”

The TV entities involved in the latest protest of the LPM service — which critics charge has troublesome fault rates and undercounts viewing by African Americans and Hispanics — are Tribune Broadcasting, Gannett Broadcasting, Post-Newsweek, NBC-Universal Television Stations. LIN-TV, Barrington Broadcasting, Liberty Corp., Fox Television Stations, Cox Television, Allbritton Communications, Fisher Communications, the Dispatch Broadcast Group, Belo, Emmis Communications, Media General Broadcast Group, E.W. Scripps and CBS. Stations owned by Allbritton, Gannett, Tribune and Fox in Washington last week failed to convince Nielsen to delay the LPM conversion in the nation’s capital.

Tribune Broadcasting President Patrick Mullen authored a letter, dated May 25, on behalf of the broadcasters, saying: “Flaws in the system must be repaired before LPM service is expanded” and that if Nielsen were to agree, it could “avoid further challenges from concerned parties.”

Nielsen President and CEO Susan Whiting replied May 27 that broadcast groups are not Nielsen’s only clients and said, “Any agreement with your group of broadcasters, or even the appearance of such, could adversely affect these different interests and subject Nielsen as well as your group of broadcasters to legal action.” She also said that a request for “mandatory, prior MRC accreditation raises considerable antitrust questions.”

Ms. Whiting suggested a conversation between Nielsen’s antitrust counsel and counsel for Mr. Mullen’s group, followed by a meeting with the MRC executive committee.