The papers, discovered when the cabinet was bought from a junk shop in Camden, north London, for £35, included a confidential memorandum to John Major, a 17-page report and the proposed design of the smart card.
The Cabinet Office said last night it would mount an inquiry once it had been confirmed the papers were genuine. But officials indicated it was possible they had been left accidentally in the filing cabinet drawer.
"We are considering the options for a smart card, and we are preparing a Green Paper on ID cards," a spokeswoman confirmed.
The Cabinet report by William Waldegrave, then Chancellor of the Duchy of Lancaster, said concerns about the smart card could be overcome if they were offered voluntarily. "The card could be issued for one primary purpose (say a driving licence), but capable of including a number of other applications (passport, benefits transfer etc) at the user's choice," Mr Waldegrave said.
Reservations about the use of national identity cards were contained in a memorandum to the Prime Minister written by Lord Wakeham, then Lord Privy Seal, who chaired a ministerial meeting on ID cards. It was written before the consultation paper on ID cards was announced at the annual Tory party conference last October.