by Steven Greenhouse

Two of New York City’s top labor leaders voiced anger on Tuesday about the agreement by Mayor Michael R. Bloomberg and Comptroller John C. Liu to overhaul the city’s pension plans.

Those union leaders — the presidents of Transport Workers Union Local 100 and Teamsters Local 237 — complained that the mayor’s and comptroller’s offices did not brief them about the proposed overhaul before it was announced two weeks ago, even though the union leaders are trustees on the city’s largest pension plan.

“I don’t know anything about the plan,” said John Samuelsen, the transit workers’ leader.

In a letter dated Monday, Mr. Samuelsen and Greg Floyd, president of Teamsters Local 237, which represents many housing authority workers, joined Bill de Blasio, the public advocate, and presidents of all the boroughs except Staten Island in asking questions about the overhaul. The union leaders’ criticism could make it harder for Mr. Bloomberg and Mr. Liu to persuade Albany to enact legislation needed for the overhaul. Mr. de Blasio and Scott M. Stringer, the Manhattan borough president, are potential mayoral candidates who may oppose Mr. Liu in the race.

Under the overhaul, the city would merge its pension plans’ five boards, which have 58 trustees, into one with about a dozen trustees that would oversee the plans’ combined $120 billion in investments. The plans cover 237,000 retirees and more than 300,000 current city and city-affiliated employees.

The mayor and the comptroller said their plan would most likely yield higher investment returns by minimizing political interference in the pension system and by naming a full-time investment manager. In their letter, the officials asked Mr. Liu to make a presentation at the next pension trustees’ meeting explaining the new board’s structure, the new trustees’ qualifications and how they would be chosen.

They also asked Mr. Liu to explain how the new plan would achieve the comptroller’s hopes of increasing annual investment returns by one or two percentage points, yielding $1.2 billion to $2.4 billion more a year and helping to hold down the city’s budget deficit.

Mr. Floyd said that a majority of the board members of the city’s main pension fund, the New York City Employment Retirement System, were also not briefed before the announcement, and he objected to the proposal to have an unelected person become the fiduciary custodian for the system, replacing the comptroller.

When the plan was announced, the mayor, several union presidents and numerous pension experts praised Mr. Liu for ceding much of his office’s power over pensions to an outside manager.

Michael Loughran, a spokesman for Mr. Liu, said, “The proposal will benefit pensioners and taxpayers alike by transforming an outdated system into a best-in-class investment vehicle.”

Mr. Samuelsen said he feared being squeezed off the new board. “Most important is the fear that we’re going to give large decision-making powers to Wall Street folks, the very people who have made horrific decisions with money over the last decade,” he said.