MI5 can currently request and receive an individual’s data but a proposal currently being considered would allow the Oyster database, and other national databases, to be opened up completely to the security services. Currently 17 million people use the Oyster card on busses, trains and the Underground.
The security services want the databases for data mining, a controversial technique which claims to be able to identify terrorists or other criminals by analysing patterns of behaviour. However it also throws up a lot of false positives.
"It's looking for a needle in a haystack, and we all make up the haystack," said former Labour minister Michael Meacher.
"Whether all our details have to be reviewed because there is one needle among us - I don't think the case is made."
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