Federal regulators accused Reserve Management and its two top executives of fraud, saying they withheld key facts from investors when its money-market fund “broke the buck” last fall.

The Securities and Exchange Commission filed a civil complaint yesterday against Reserve Management, its chairman, Bruce Bent Sr., and its vice chairman and president, Bruce Bent II.

The SEC said the pair failed to provide “key material facts” about the shaky situation of Reserve’s Primary Fund after Lehman Brothers filed for bankruptcy protection in September.

New York-based Reserve Management said it “intends to defend itself vigorously” against the SEC’s allegations. “We are hopeful that this matter can be resolved quickly,” Bruce Bent Sr. said in a statement issued by the company.