LOS ANGELES, AUG. 28 -- Leaders of major police and prosecutor groups met with President Reagan today and launched a national campaign to persuade the U.S. Senate to confirm Judge Robert H. Bork to the Supreme Court.

Led by Illinois Gov. James R. Thompson (R), a former federal prosecutor, the group representing most major law enforcement associations said they would ask their hundreds of thousands of members to call and write key senators with praise for Bork.

Thompson lauded Bork's past decisions upholding criminal convictions despite accusations of police misconduct and called him "one of the most evenhanded, clear thinkers in the history of U.S. jurisprudence."

Thompson said the unusual lobbying campaign by politically influential police groups was sparked by an equally unusual amount of anti-Bork organizing and lobbying by civil rights and women's groups. Senate Judiciary Committee Chairman Joseph R. Biden Jr. (D-Del.), who has scheduled hearings on the nomination beginning Sept. 15, has already announced he will oppose elevating the conservative U.S. Court of Appeals judge to the high court.

White House officials have said they think Bork can win Senate support, but expect a close vote. Reagan welcomed the law enforcement leaders at a meeting in the Century Plaza Hotel here today and said through his spokesman, Marlin Fitzwater, that he plans to meet with other groups attracted to other parts of Bork's record.

Shortly before the president met with the group, four attorneys active in public-interest law in California held a news conference here charging that Bork's views on criminal justice were unclear and that he seemed to take "an extremely lenient approach to violations of the law by corporations and executive branch officials alike."

"Judge Bork does not believe in law and order," said Loyola Law School professor Karl Mannheim. "He sees his judicial role as one of promoting big business."

The anti-Bork group distributed an analysis of Bork's appeals court criminal decisions. It said most of the cases he reviewed involved drugs and "have been so straightforward and noncontroversial that even the court's most 'liberal' members have sided with the prosecution."

The White House, however, distributed a "fact sheet" today on Bork's criminal law views that mentioned several cases he argued when serving as U.S. solicitor general in the Nixon administration. At that time he defended the death penalty and sought to weaken the impact of the exclusionary rule, which bars use of evidence improperly gathered by police.

Thompson said he thought Bork's views on criminal justice were clear. He cited an article in which Bork suggested shifting the correction system's emphasis from rehabilitating felons in prison to improving their opportunities at the time they are released.

In the face of accusations that Bork's rulings have mirrored his personal ideology, rather than the law, Thompson repeatedly emphasized the judge's "evenhandedness" and "open-mindedness." "People change their minds over the course of time," Thompson said. "When I was in law school, I was a staunch liberal; then I became a prosecutor and I saw the other side."

Robert Bonner, the U.S. attorney in Los Angeles and one of the officials who met with Reagan, said it was important that Bork felt "the rights of the defendant not be paramount to the rights of the victim."

Also attending the meeting, and endorsing Bork, were representatives of the 200,000-member Fraternal Order of Police, the 50,000-member National Troopers Coalition, the International Association of Chiefs of Police, the National Sheriff's Association, the National District Attorneys Association, the International Narcotics Enforcement Officers Association and the National Law Enforcement Council.

"For the past seven years," Reagan told the group, "federal criminal sentences have increased 30 percent overall. Judge Bork's nomination is a crucial opportunity to continue our progress in the war against crime."