'THEY DON'T HAVE A CHOICE'

Alexander said it was important to keep in mind that companies were compelled by US law to hand over data.

"They don't have a choice. Court order, they have to do this," he said.

"From my perspective, what they want is the rest of the world to know that we're not reading all of that email, so they want to give out the numbers. I think there's some logic in doing that."

The letter also asked Congress to pass legislation that would require the federal government to make transparency reports and let companies disclose user data requests without having to ask a court for permission.

Co-signers included investors such as Boston Common Asset management and Union Square Ventures, as well as scores of associations including Human Rights Watch, Electronic Frontier Foundation, the American Civil Liberties Union, Americans for Tax Reform and conservative FreedomWorks.

One of the lawmakers to whom the letter was addressed was Senate Judiciary Committee Chairman Patrick Leahy, a Democrat who has introduced a bill that would expand reporting requirements for the secret programs, add more court reviews and move up the expiration of the authorization for some of the data collection by 2 1/2 years.

"Americans deserve to know how much of their communications data is being swept up by government surveillance, and the government's use of these authorities must be subject to strong oversight," Leahy said on Thursday.

He said the Judiciary Committee would hold another hearing on the issue later this month.

The White House and Department of Justice did not immediately comment on Thursday's letter.