The councilman, Daniel J. Halloran, became something of a national news celebrity for a more than week. Commentators said his evidence showed how public employee unions were harming America.
But on Friday, a report by the city’s Department of Investigation said that investigators, after interviewing more than 150 witnesses and reviewing video from surveillance cameras and from angry residents, had found no evidence of an organized slowdown. In fact, the report found, Mr. Halloran had no evidence for his accusation, and his account of conversations with two workers differed sharply from what the workers told investigators.
“In toto,” the report said, “Mr. Halloran’s information about city employee statements contributed no actual evidence about a possible slowdown.”
The report did find fault with elements of the city’s response to the Dec. 26 snowstorm, which left 20 inches of snow in Central Park and paralyzed the city for days. A half-dozen trucks, among hundreds reviewed, were inexplicably idle, or moving through snowbound streets with their plows raised for no apparent reason. Some workers remained with stuck vehicles for as long as 12 hours, investigators found. About 44 percent of the snow chains on trucks broke during the cleanup.
And a few workers were photographed buying beer or coffee when they were supposed to be cleaning the streets. The investigators said those workers were doing so only while stuck with broken-down equipment, and not as part of a labor slowdown, but the workers caught drinking now face disciplinary charges.
The city also made choices that might have slowed the cleanup. A decision to stop salting roads as the snowfall warnings increased was controversial within the Sanitation Department. And because the city elected not to declare a snow emergency, many drivers became stuck in roadways, and their cars impeded the cleanup.
Mayor Michael R. Bloomberg, who initially dismissed complaints about the storm response, said through a spokeswoman on Friday that many of the new report’s findings would be addressed “to ensure that snow removal operations function well in the future, as they have in many other storms.”
Harry Nespoli, the president of the sanitation workers union, said the report vindicated his members and supported what he had said in testimony to the City Council and in numerous news media interviews in the weeks after the storm.
“The report confirms my contention that the members of this union would never participate in an organized action that puts our city and its people at risk,” Mr. Nespoli said in a statement.
Mr. Halloran released a statement through his spokesman pointing out that while the investigation found no evidence of a slowdown, it did not “come to any definite conclusion” that one did not happen.
“I am proud that my constituents felt I would have the courage of my convictions to take on the city,” the statement said. “They expect me to stand up for them and be their voice and I am going to keep doing that.” Mr. Halloran had been quoted saying that workers had come to his office during the storm and told him they had been directed to take part in a slowdown to embarrass Mr. Bloomberg, who had proposed work force changes in the Sanitation Department.
Mr. Halloran has said he based his slowdown accusations, which first appeared in The New York Post, on conversations he had with two Transportation Department supervisors who had been assigned to the cleanup and with three Sanitation Department workers.
But he refused to give the names of the sanitation workers to investigators, citing attorney-client privilege. A footnote in the report notes that after Mr. Halloran raised attorney-client privilege as a basis to withhold information, a Department of Investigation lawyer informed him that city conflict-of-interest rules bar public servants from doing work that “is in conflict with the proper discharge of his or her official duties."
When city investigators spoke to the transportation supervisors, the two said they had no evidence of a slowdown.
One said he did not reach out to the councilman, as Mr. Halloran had said, but had been summoned to his office by a mutual friend. The supervisor, who was not named in the report, said he submitted to a brief “grilling” by Mr. Halloran, but told the councilman that he knew nothing about a slowdown other than the rumors he had heard in the news media.
The supervisor said Mr. Halloran appeared to be upset with that answer.
The other supervisor also said he knew nothing about a slowdown and was present only because he had happened to tag along with his colleague. He said Mr. Halloran appeared annoyed.
According to the report, one of the transportation supervisors told investigators that as they were leaving the meeting, Mr. Halloran said, “If you don’t want to talk, I will find a disgruntled worker who is ready to retire who is.”
In February, Mr. Halloran was called to testify before a grand jury investigating the supposed slowdown. No announcements have been made about whether its investigation has concluded. A spokesman for Loretta E. Lynch, the United States attorney in the Eastern District of New York, declined to comment.