The Senate's top Democrat says Veterans Affairs Secretary Jim Nicholson should resign, calling his leadership a threat to national security after the VA lost another computer containing veterans' personal data.

"Enough is enough," Senate Minority Leader Harry Reid, D-Nev., said Tuesday. "Less than a month after promising to make the VA the 'gold standard' in data security, Secretary Nicholson has again presided over loss of the personal information of thousands more veterans."

Reid is the third Senate Democrat — joining Sens. Patrick Leahy of Vermont and John Kerry of Massachusetts — who has called for Nicholson's ouster following high-profile data thefts at the government's second largest agency.

"Unfortunately, this dangerous incompetence has become all too common in the Bush White House, and it has made America less safe," Reid said.

VA spokesman Matt Burns dismissed the statements as "political opportunism."

"It's nice to see that political season is in full swing," Burns said. "Unfortunately, angry personal attacks and political opportunism accomplish nothing in the way of providing solutions to the important issues facing our nation's veterans."

On Monday, the VA announced that one of its subcontractors, Unisys Corp., had lost a desktop computer containing personal data for as many as 38,000 veterans who received care at VA medical centers in Philadelphia and Pittsburgh. The computer was located at Unisys' offices in Reston, Va.

Federal and local authorities were investigating the incident, which is believed to involve veterans' names, addresses, Social Security numbers, dates of birth, insurance carriers and claims data including medical information.

The disclosure came two days after authorities said they had arrested two teens in connection with the May 3 theft of a laptop and external drive containing the personal data of 26.5 million veterans at a VA employee's home in suburban Maryland.

On Tuesday, lawmakers from both parties criticized the latest data loss, which they said needlessly put veterans and active-duty troops at risk of identity theft.

In recent weeks, the VA has also acknowledged losing sensitive data for more than 16,000 veterans in at least two other cases in Minneapolis and Indianapolis.

Leahy said it was time for Bush to hold Nicholson accountable. In May, White House press secretary Tony Snow said Bush had "full faith and confidence" in Nicholson's leadership.

"Certainly, our nation's veterans, who have been willing to make the ultimate sacrifice for their country, deserve better," Leahy said.

Kerry said, "Fire the incompetents. ... Losing veterans' most sensitive personal information must have consequences."

Senate Republicans were less critical, saying Nicholson deserved a chance to fix the department after becoming VA secretary less than two years ago.

"It is clear that there is a systems problem with VA data security which must be fixed," said Sen. Larry Craig, R-Idaho, who chairs the Senate Veterans Affairs Committee. "But calling for Secretary Nicholson's resignation is over the top. It does not and will not solve the problem."

Click here to visit FOXNews.com's Identity Theft Center.