Disgraced former state Assembly Speaker Sheldon Silver was indicted on federal corruption charges Thursday — and authorities vowed to hold his hefty pension hostage if he’s convicted and can’t pay back his alleged ill-gotten gains.

For the past 15 years, Silver “engaged in a secrete and corrupt scheme to deprive the citizens of the state … by using the power and influence of his official position to obtain for himself millions of dollars in bribes and kickbacks,’’ Manhattan US Attorney Preet Bharara said in the indictment.

Silver is accused of illegally pocketing a total of nearly $4 million in the alleged scheme — and may have to cough up his pension if he is found guilty in order to make restitution, Bhahara warned.

For Silver, who has served 38 years as an assemblyman, that would mean a $87,120 annual pension — or an estimated total $1.15 million over his expected life span, according to the Albany-based think tank Empire Center for Public Policy.

Also at stake are the hundreds of thousands of dollars that Silver has stashed in multiple bank accounts, as well as his several properties, the indictment said.

Silver’s property holdings include two Lower East Side co-op apartments at 550 Grand St. and a Catskills country getaway in upstate Woodridge.

Although politicians have historically been able to keep their pensions after being convicted of felonies, in 2013, Bharara began a campaign to go after the dough in order to make restitution.

The three-count indictment charged Silver with wire fraud, mail fraud and extortion. Each count carries 20 years behind bars.

He had been arrested Jan. 22 amid charges he collected $3 million alone in kickbacks for steering asbestos-related cancer cases from a leading Manhattan oncologist to the Weitz & Luxenberg law firm.

To pay off the cancer doctor allegedly involved, Silver is suspected of funneling two state research grants of $250,000 each to him.

Silver is set to be arraigned Tuesday afternoon before Manhattan Federal Judge Valerie Caproni.

His lawyers said he would plead “not guilty.”

“We can now begin to fight for his total vindication. We will do our fighting where it should be done: in court,” Silver’s lawyers, Joel Cohen and Steven Molo, said in a statement.

Silver’s stunning arrest and indictment capped a secret grand-jury probe that began in June 2013 and marked the latest in a string of public corruption cases spearheaded by the crusading Bharara.

Although he remains on the Assembly, Silver gave up his powerful speaker post Feb. 2 at the urging of fellow state Democratic Party leaders.

© 2015 New York Post