NEW YORK — NBA referees, influenced by cozy relationships with league officials, rigged a 2002 playoff series to force it to a revenue-boosting seven games, a former referee at the center of a gambling scandal alleged today.

Without identifying anyone or naming teams, Tim Donaghy also claimed the NBA routinely encouraged refs to ring up bogus fouls to manipulate results but discouraged them from calling technical fouls on star players to keep them in games and protect ticket sales and television ratings.

Speaking before the start of the NBA finals Game 3 featuring the Los Angeles Lakers and Boston Celtics, NBA commissioner David Stern called the allegations baseless.

"All I can say is that he's looking for anything that will somehow shorten the sentence, and it's not going to happen," Stern said.

The allegations were contained in a letter filed by a lawyer for Donaghy, who pleaded guilty last year to felony charges alleging he took cash payoffs from gamblers and bet on games himself. The 41-year-old Donaghy faces up to 33 months in prison at sentencing on July 14.

"If the NBA wanted a team to succeed, league officials would inform referees that opposing players were getting away with violations," the letter said. "Referees then would call fouls on certain players, frequently resulting in victory for the opposing team."

The league called Donaghy's allegations false and self-serving, saying the scandal was limited to him and two co-defendants, both former high school classmates who also pleaded guilty to gambling charges.

Donaghy's lawyer has sought to convince a federal judge in Brooklyn that Donaghy, of Bradenton, Fla., deserves more credit for coming forward before he was charged to disclose behind-the-scenes misconduct within the NBA. The letter, filed Monday, suggests prosecutors have hurt Donaghy's chances for a lesser prison term by downplaying the extent of his cooperation.

Donaghy's attorney, John Lauro, and prosecutors declined comment.

"He's a singing, cooperating witness who is trying to get as light a sentence as he can," Stern said. "He turned on basically all of his colleagues in an attempt to demonstrate that he is not the only one who engaged in criminal activity. The U.S. attorney's office, the FBI, have fully investigated it, and Mr. Donaghy is the only one who is guilty of a crime. And he will be sentenced for that crime regardless of the desperate attempts to implicate as many people as he can."

In one of several allegations of corrupt refereeing, Donaghy said he learned in May 2002 that two referees known as "company men" were working a best-of-seven series in which "Team 5" was leading 3-2. In the sixth game, he alleged the referees purposely ignored personal fouls and called "made-up fouls on Team 5 in order to give additional free throw opportunities for Team 6."

"Team 6" won the game and came back to win the series, the letter said.

Only the Los Angeles Lakers-Sacramento Kings series went to seven games during the 2002 playoffs. And the Lakers went on to win the championship.

At the time, consumer advocate Ralph Nader and the League of Fans, a sports industry watchdog group, sent a letter to Stern complaining about the officiating in Game 6 of the Western Conference finals.

The Lakers, who beat Sacramento 106-102 in that game in Los Angeles, shot 27 free throws in the final quarter and scored 16 of their last 18 points at the line.

The letter also alleged manipulation during a 2005 playoff series.

"Team 3 lost the first two games in the series and Team 3's owner complained to NBA officials," the letter said. "Team 3's owner alleged that referees were letting a Team 4 player get away with illegal screens. NBA Executive Y told Referee Supervisor Z that the referees for that game were to enforce the screening rules strictly against that Team 4 player. ... The referees followed the league's instructions and Team 3 came back from behind to win the series. The NBA benefited from this because it prolonged the series, resulting in more tickets sold and more televised games."

In that same series, the letter says "Team 3" lost the first two games of the series and that team owner complained to NBA officials. The letter also alleges that the opposing team's coach later was fined $100,000 after revealing an NBA official informed him of the behind-the-scenes instructions.

That would correspond with the 2005 first-round playoff series between the Houston Rockets and the Dallas Mavericks, in which Mark Cuban complained to officials and Jeff Van Gundy was fined.

Donaghy's letter said that in the first of several meetings with prosecutors and the FBI in New York in 2007, he named names while describing "various examples of improper interactions and relationships between referees and other league employees, such as players, coaches and management." For example, it said, referees broke NBA rules by hitting up players for autographs, socializing with coaches and accepting meals and merchandise from teams.

"The NBA remains vigilant in protecting the integrity of our game and has fully cooperated with the government at every stage of its investigation," Richard Buchanan, NBA executive vice president and general counsel, said in a statement. "The only criminal activity uncovered is Mr. Donaghy's."

Donaghy, who pleaded guilty last year to charges he conspired to engage in wire fraud and transmitted betting information through interstate commerce, has said he made NBA bets for four years, even wagering on games he worked. He also admitted recommending bets to high-stakes gamblers and collecting $5,000 if his picks hit.