Ex-Assembly Speaker Sheldon Silver has subpoenaed key documents from a doctor who allegedly took $500,000 worth of state cancer-research grants in exchange for referring patients to Silver’s law firm, new court papers reveal.

Dr. Robert Taub has been ­ordered to appear in Manhattan federal court with records involving “grants received, awarded or applied for from 2000 through the present,” and “referrals provided to law firms, including . . . Weitz & Luxenberg,” the firm with which Silver was affiliated.

Silver allegedly funneled Taub the grant money and in return Taub sent the firm patients suing for asbestos-related illnesses.

The patient referrals earned Silver more than $3 million in kickbacks from the firm, prosecutors allege.

Taub’s lawyer wants the subpoena quashed.