More than 4,000 NHS smartcards used to access a range of electronic systems and applications have gone missing since they were introduced two and a half years ago.
A freedom of information request by GP magazine Pulse found a total of 4,147 smartcards have been lost, 142 of which have been stolen.
Of the 221 NHS bodies that replied to the freedom of information request, one in 10 said they had no idea how many cards had been lost or stolen.
A Connecting for Health spokeswoman told ZDNet.co.uk sister site silicon.com that, as soon as lost cards are reported, they are disabled. She added that active cards require a unique six-digit PIN number known only by their owner.
In a statement, Connecting for Health said there is "no evidence that any security breaches have ever arisen from lost or stolen cards".
The spokeswoman added there are no plans to change the system as a result of the findings.
The smartcards have been issued to 438,314 NHS staff since their introduction in mid 2005, with around 1.2 million staff expected to eventually carry one.
The smartcards are used to access systems such as Choose and Book and the Electronic Prescription Service.