This photo taken Tuesday, March 12, 2013, shows Director of National Intelligence (DNI) James Clapper, right, testifying before the Senate Intelligence Committee during the annual open hearing on worldwide threats on Capitol Hill in Washington. Clapper has decried as reckless the revelation of the National Security Agency's intelligence-gathering programs by former NSA and CIA contractor, Edward Snowden, and said it has done "huge, grave damage." A DNI spokesman said intelligence officials are "currently reviewing the damage that has been done by these recent disclosures." (AP Photo/Susan Walsh) 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.

The senators also cited Clapper's much-scrutinized claim before the programs were revealed that the government wasn't collecting bulk data on millions of Americans. They say misleading statements and secret decisions have “prevented our constituents from evaluating the decisions that their government was making, and will unfortunately undermine trust in government more broadly. The debate that the President has now welcomed is an important first step toward restoring that trust.”

The letter includes seven specific questions that the senators would like Clapper to answer.

The senators who signed the letter are: Wyden, Mark Udall (D-Colo.), Lisa Murkowski (R-Alaska), Patrick Leahy (D-Vt.), Mark Kirk (R-Ill.), Dick Durbin (D-Ill.), Tom Udall (D-N.M.), Brian Schatz (D-Hawaii), Jon Tester (D-Mt.), Jeanne Shaheen (D-N.H.), Dean Heller (R- Nev.), Mark Begich (D-Alaska),  Bernie Sanders (I-Vt.), Patty Murray (D-Wash.), Jeff Merkley (D-Ore.), Mazie Hirono (D-Hawaii), Al Franken (D-Minn.), Tom Harkin (D-Iowa), Chris Coons (D-Del.), Maria Cantwell (D-Wash.), Richard Blumenthal (D-Conn.), Max Baucus (D-Mont.), Elizabeth Warren (D-Mass.), Martin Heinrich (D-N.M.), Tammy Baldwin (D-Wisc.) and Mike Lee (R-Utah).

The letter can be downloaded here.