Tesco plans to roll out Electronic Article Surveillance systems across its portfolio apart from Express stores by Autumn.
It has already has the security system in 300 stores, said a spokesman, and has "every confidence in it".
But some shrinkage experts say EAS systems don't give returns on investment ­ likely to be several millions of pounds in the case of a major multiple.
EAS systems set off an alarm at the door if a shopper takes a tagged item through which has not been deactivated. Generally, higher value items are tagged. But false activations, for example by library books, are common.
Dr Paul Chapman, senior research fellow at Cranfield School of Management said EAS systems would not deter a seasoned shoplifter.
He said: "EAS systems claim to reduce shrinkage. There are literally hundreds of ways that shrinkage can occur.
"Off-shelf theft by customers is but one."
Retailers' estimates compiled by ECR Europe suggest supplier fraud accounts for 12% of stock loss, process failures 27%, external theft 37%, and internal theft 24%.

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