Some Tesco customers who have been overcharged were not being reimbursed in the way the company promised, the Director of Consumer Affairs, Ms Carmel Foley, said yesterday.

She stated that inspectors from her office had found "evidence" that some Tesco store managers were not adhering to the company's "no quibble" policy - where overcharged customers were given the item for free and all the money paid was refunded.

Instead, customers in some stores were given the difference between the price charged and the price on the shelf, she said. She contacted Tesco last night to ask why some staff seemed unaware of the "no quibble" policy.

She said during discussions with the company's management last week she was told the policy meant customers had all their money refunded. "This is not happening in many cases we have investigated," she said.

A spokeswoman for Tesco confirmed Ms Foley had contacted the company and in response the "no quibble policy" would be "restated to all staff". She said the company was making progress in eliminating pricing errors.

However, one customer who contacted The Irish Times claimed he was overcharged when he bought tomatoes in a Tesco store in Dublin yesterday.

The deputy store manager accepted the customer paid a price different to the one displayed, but said this occurred because staff failed to take down the special offer price over the weekend. Meanwhile, inspectors from Ms Foley's office have started a series of spot checks on stores to see whether overcharging is a widespread practice. Ms Foley said preliminary results from the spot checks should be available by Friday.

She confirmed that her office had received complaints of overcharging by several retailers, not just Tesco in recent weeks. She declined to comment on who was the subject of most complaints.

Ms Foley said she was currently considering prosecutions against some retailers. However, it is understood many consumers who made complaints to her office are reluctant to sign affadavits necessary for any prosecution.

She has requested that Tesco publish an advertisement explaining what actions it has taken on the overcharging issue by the end of the week. A further meeting with the company is also scheduled after Easter to check on what progress has been made.

The investigation into allegations that Superquinn asked its suppliers for "hello money" was continuing, said Ms Foley, with most of the work concentrating on Retail Logistics - the company to which suppliers made their payments.

"There is a lot of detail over several years to piece together," she said. She said a newspaper report suggesting that her office has arrived at a conclusion about the matter, was "without foundation".