Director of National Intelligence James Clapper told a Senate panel that an estimated 70% of intelligence workers had been placed on unpaid leave.
Also, the head of the US electronic spy agency said morale had been devastated.
The US government closed non-essential operations on Tuesday after Congress failed to reach a new budget deal.
Leahy, a Democrat who is drafting legislation to reform US government surveillance, pressed Alexander and Clapper on the accuracy of their previous testimony.
"Both of you have raised concerns that the media reports about the government's surveillance programs have been incomplete, inaccurate, misleading," Leahy said. "But I worry that we're still getting inaccurate and incomplete statements from the administration."
He drew attention to repeated claims by the intelligence agencies that 54 terrorist attacks had been thwarted by two particular programs.
"That is plainly wrong, but we still get it in letters to members of Congress, [and] we get it in statements," Leahy said. "These weren't all plots, and they weren't all thwarted. The American people are getting left with inaccurate reflection of the NSA's programs."
Alexander then conceded that the 54 examples were "not all plots" and only 13 had a nexus in the US. He also admitted there were only "one or possibly two" cases of terrorist activity that would not have been prevented "but for" section 215 of the Patriot Act, which authorises bulk phone record collection.
For those that would like to see Clapper live... Sounds like a set-up for an attack...
reply to post by smurfy
From the outside it looks like they are using intelligence collection to serve corporate interests, it is well known some of those Congress folk make five percent more than the hedge fund managers.