On Friday last week the MoD admitted that 658 of its laptops had been stolen over the past four years - nearly double the figure previously claimed.

The department also said 26 portable memory sticks containing classified information had been either stolen or misplaced since January.

However, the MoD insisted its policies were “generally fit for purpose”, and said all data losses were fully investigated.

The embarrassing new details were disclosed by ministers in response to questions tabled in Parliament.

Previously the MoD had confessed to 347 laptops being stolen between 2004 and 2007.

But Defence Secretary Des Browne was forced to issue revised figures after “anomalies in the reporting process” were discovered.

The official total is now 658 laptops stolen, with another 89 lost. Thirty-two have been recovered.

In a separate response, ministers said 121 of the department’s USB memory sticks had been taken or misplaced since 2004.

Some 26 of those went this year - including three which contained information classified as “secret” and 19 which were “restricted”.

In the latest laptop theft on Thursday, the official had placed the laptop on the ground at the Liverpool hotel when it was stolen, an MoD spokesman said.

When asked on Sunday whether that brought the total number of laptops stolen to 659, the spokesman said: “Yes, I think so.”

Last month the MoD was heavily criticised by a review of its data procedures which warned that basic security discipline had been forgotten and there was “little awareness” of the danger of losing information.

But a spokeswoman for the department said on Friday: “Any loss of data is investigated fully.

“The recent report on data losses by Sir Edmund Burton found that MoD policies and procedures are generally fit for purpose, but also identified a number of areas where MoD needs to do better in protecting personal data.

“MoD has developed, and is now working through, an action plan to address all of the report’s recommendations and bring the department’s handling of personal data to an acceptable state.”