James Clapper (AP Photo)

A group of 26 senators have signed a letter demanding that National Intelligence Director James Clapper publicly answer questions about the federal government's bulk collection of data -- one of the broadest efforts yet to apply pressure on the intelligence community in the aftermath of the disclosures of its surveillance programs.

Sen. Ron Wyden (D-Ore.) organized the effort, which has the support of a bipartisan group of senators comprising more than one-quarter of the chamber -- a significant statement from privacy advocates in the Senate.

“We are concerned that by depending on secret interpretations of the PATRIOT Act that differed from an intuitive reading of the statute, this program essentially relied for years on a secret body of law,” the senators wrote in the letter.