The two lost HM Revenue & Customs CDs containing the personal and financial details of 25 million people could be worth £1.5bn to criminals.
Liberal Democrat acting leader Vince Cable, speaking in the House of Commons, said a single stolen identity is worth £60 on the black market.
He said: "We are therefore considering a stock of criminal value of around £1.5bn, which makes the Brinks Mat robbery the equivalent of stealing the church collection. An enormous amount remains at stake."
But chancellor of the exchequer Alistair Darling said: "The police inform me that they still have no evidence or intelligence that this data has fallen into the wrong hands and no evidence of fraud or criminal activity."
Cable also slammed the failure to use encryption technology to secure the data on the lost CDs and said most data being shipped around in government is not being encrypted.
He said: "Encryption is simply not happening. What are the reasons for that? My understanding, from talking to some of the specialists involved, is that IT specialists, mostly freelancers, are needed to encrypt data. The big IT companies are not interested in using them and the civil servants who oversee them do not understand the problem, so encryption is not happening."
Darling faced another grilling from MPs and was accused by shadow chancellor George Osborne of not telling the public the "whole truth" about the loss of the two CDs in Darling's original statement last week.
But Darling responded: "That statement was accurate in every respect in accordance with the information that I had then and have today. I specifically said in my statement that the House would understand that because the investigation was continuing, I was not yet in a position to give a full account of what had happened."