The MTA has approved an 8 percent salary increase for managers through next year -- weeks after reaching agreement to give raises to most union workers.

In a memo to the agency's top brass sent Wednesday, Metropolitan Transportation Authority chairman Thomas Prendergast authorized all full-time, non-union represented employees to receive "an upward adjustment to their base salary" of 4 percent, retroactive to Jan. 1, 2013.

MTA spokesman Adam Lisberg confirmed Saturday that the plan would includes another 2 percent raise this year and next year, for a total salary increase of 8 percent.

The raise would only be given to management workers "who have satisfactory performance," and would not include agency heads, whose salaries are negotiated separately, Prendergast said in his memo.

Lisberg said the non-union workers, which comprise 8,000 of the agency's 68,000-member workforce, have not received a raise in six years. The raises, which will cost the MTA about $50 million a year, account for about 0.6 percent of the agency's total annual labor costs of $8 billion, Lisberg said.

"Sooner or later, people deserve a raise," Lisberg said.

Union leaders, during contentious contract negotiations, disputed the MTA's assertion that managers have had their salaries frozen for six years. They accused the agency of routinely disguising management pay bumps as promotions, title changes, or expansions of duties.

In December, a panel of mediators assigned by President Barack Obama to review a labor dispute involving Long Island Rail Road unions agreed that such "ad hoc" raises "have increased the pay for a substantial number of management personnel."

Prendergast waited on approving the raises until after settling the contract disputes with most MTA unions. In April, the MTA reached a pack with its largest labor organization, the Transport Workers Union, to give about 35,000 New York City Transit subway and bus workers raises of 8 percent over five years.

Thomas Creegan, a TWU union officer, said the 8 percent, two-year management raises prove the agency "ripped . . . off" laborers.

"How do you have that kind of money?" said Creegan, a subway third-rail chairman, who noted that the 8,000 managers account for more than the entire LIRR labor force of less than 6,000. "It's unheard of. Absolutely unheard of. Obviously, the money is there."

Lisberg noted that, unlike union workers, managers will not be made whole for the years they went without raises before 2013. He also noted that the managerial workforce, which includes secretaries and other administrators, have also seen layoffs and major cost-cutting in recent years.

"If he [Creegan] thinks that managers did not make sacrifices and did not take cuts . . . I think he should talk to some people who were laid off," Lisberg said.

In July, three days before a strike deadline, Gov. Andrew M. Cuomo brokered a deal to give more than 5,000 LIRR laborers raises totaling 17 percent over 6.5 years, including an immediate 11 percent bump retroactive to 2010.

Prendergast's memo did not address future raises for MTA managers, but the agency's recently released financial plan assumes "wage-inflation for non-represented employees" averaging about 1.85 percent through 2018.