Israel’s Chief Rabbinate is turning to barcode technology in the Passover struggle against leavened products.

Every year, Israeli supermarkets with a kashrut certificate “sell” all the chametz products in stock to a non-Jew on the eve of the festival. The nominal sale is automatically cancelled when Pesach ends and the chametz reverts to the supermarkets’ ownership.

During the week-long festival, most of the chametz goods remain on covered-up shelves.

In many stores, shoppers can simply reach under the covers, take out chametz and pay for it at the tills.

The Chief Rabbinate is fighting back against this rule-bending by writing to the supermarket chains and asking them to use a computer program that will block the bar-codes of chametz products, thus banning their sale. Most chains have resisted, citing technical and legal reasons, and complaining that the technology was introduced too late.

So far, the Chief Rabbinate has not threatened the supermarkets with the loss of their certificates, but Rabbi Yaakov Sabag, head of the kashrut department, warned that the Rabbinate may publicise which supermarkets are selling chametz.

The supermarket chains are reluctant to engage in open conflict with the Rabbinate, but argue that the new programme is unfeasible. “We make every effort to keep our stores kosher,” said one senior executive. “But messing with our barcode software will cause us untold damage.

“We have done everything that the Rabbinate has asked in the past, but we can’t stop customers taking products from covered shelves, though we don’t encourage them to do so.”

Sources in the Chief Rabbinate acknowledged this week that they handled the situation badly.

“We notified the supermarket chains only a few weeks before Pesach,” said one rabbi, “and it obviously was too late by then. Next year, we will approach them much earlier. We can’t allow this farce — whereby supermarkets with a certificate sell chametz throughout Pesach — to continue.”