Prince George's County Assistant Police Chief Joseph D. Vasco Jr. yesterday branded as "at least 50 percent . . . inaccurate" a quote attributed to him in The Washington Post last year that suggests he thought it was proper for police to stage robberies in 1967 to catch suspects.

Vasco's comment came in a federal court trial here in which he is a defendant with two other county police officials in a $9 million civil rights lawsuit accusing them of setting up a series of so-called "death squad" robberies and burglaries in which two suspects were shot and killed by waiting police, a third was wounded and seven others arrested.

Barnet D. Skolnik, an attorney representing plaintiffs against the police, asked Vasco if he was accurately quoted in a July 28, 1982, Post article, noting that "the central allegation of this lawsuit is that you helped set up armed robberies by instructing informants to solicit others to commit the robberies."

The article quoted Vasco as saying, "You have to understand that these are the kind of things that were done. I mean, the kind of police work that was done 15 years ago in a different era, a different culture. There was nothing wrong with it then. I mean, there's nothing wrong with it now."

Vasco replied in court today, "At least 50 percent of what The Washington Post quoted me as saying is totally inaccurate."

Attorneys for Vasco immediately objected to Skolnik's reference to the Post article, noting that it is not clear from the context of the quote what specific "things" Vasco acknowledged doing as a police officer in 1967. Presiding Judge Herbert F. Murray agreed and ordered Skolnik to stop questioning Vasco about the quote.

The issue of which specific "things" Vasco may have been acknowledging is crucial to police lawyers in the trial. While they strongly deny the central accusation that Vasco and others instructed informers to recruit acquaintances for crimes, they have conceded related police actions, such as suggesting changes in time and location of planned crimes that informers tipped them to and providing "instrumentalities" for the crimes, such as a key to a store or a getaway car.

Police contend that changes in time and location are justified to minimize possible harm to innocent bystanders at stores staked out by undercover officers. Providing a car or a key is constitutionally permissible, they say, if the suspects are predisposed to commit the crime and planned it themselves.