The city of Philadelphia today sued the Washington Post Co. for libel because of an article it published last week critical of the city's police force.

During a city hall press conference, city solicitor Sheldon L. Albert charged The Post and reporter Jonathan Neumann with malice. Albert asked the U.S. District Court in Philadelphia to aware the city $20 million.

"Mr. Neumann knew his articles were inaccurate," Albert said.

Neumann's Aug. 14 article came the day after the Justice Department filed suit against Philadelphia charging top city officials, including Mayor Frank Rizzo, with condoning police brutality.

Albert charges that Neumann's article contained "false and untrue statements," including its first paragraph, which said, ". . . than 20 Philadelphians watched in stunned disbelief as 10 policemen beat a black man, breaking nightsticks on his head and shoulders, after he had run a stop sign."

Post managing editor Howard Simons said the newspaper's attorneys had not yet seen Albert's allegations. "I stand by Jon Neumann's story," Simons said.

In 1977 Neumann was a member of the Philadelphia Inquirer team that won a Pulitzer Prize for a series of stories about police brutality.

Albert also threatened to sue syndicated columnist Carl T. Rowan. In a column that appeared Sunday in a local paper, Rowan wrote, "Philadelphia's lower officials have become part of an unspoken conspiracy to condone the worst examples of police brutality in America since the days when policemen were part of and protective of a Ku Klux Klan that had an unwritten license to murder and maim."

The column represented "the same deliberate and corrupt journalism that appeared in The Washington Post," Albert said.

Rowan said Albert's action was "an obvious attempt to try to intimidate the press.

"I will not be intimidated. My column was accurate and reasonable and I stand by it."

Although Albert said he is confident of a legal victory, there is some doubt about a city's standing in suing for libel.

Herbert B. Newberg, a Philadelphia lawyer specializing in group litigation, said "courts generally do not recognize as proper and valid" cases where a group, in this case the city of Philadelphia, claims to have been harmed in print.

He said that plaintiffs generally must show that an individual has been harmed in order to have standing. Twice previously Rizzo has backed away from legal action against the news media. In January 1978, he dropped a $6 million libel suit against the Philadelphia Inquirer. That followed a satirical column written about the mayor.

Earlier this year Rizzo threatened, then decided against suing the Public Broadcasting Service and its local affiliate. Then he charged the city and its Italian-American community were slandered by a documentary entitled "Rizzo."