Judith McEwan, of Earlsfield Road, London, is the sole director of Absolutely Divine, a jewellery company which supplied "nickel-free" earrings to the Tutti store in Artizan Road, Northampton.

McEwan pleaded guilty yesterday to three counts of breaking the Consumer Protection Act and four counts of breaking the Trade Description Act.

The court heard that, on June 26 last year, Anita Solan, the manager of the Tutti store, sold a pair of earrings to a woman who had explained she was highly allergic to nickel and who was shown a sign asserting the jewellery was nickel-free.

Claire Bates, prosecuting on behalf of Northamptonshire County Council Trading Standards, said: "When the customer got home and put the earring in, she had a severe reaction within 10 minutes. She approached the shop and requested a refund, but was told because the earrings had been worn that it would not be possible."

After contacting Consumer Direct, trading standards officers began an investigation into the store and purchased several items of jewellery undercover, for testing.

Mrs Bates said: "In some cases, the level was 100 times the legal limit."

McEwan, defending herself, said she was also allergic to nickel and that the American company from whom she bought the jewellery, Sweet Romance, had always assured her and provided documentation that the products were nickel-free.

The 60-year-old said once she learned there was a problem, she had the jewellery tested and found it contained illegal levels of nickel.

She added: "I believe the staff and new management of the American company which supplies the jewellery to me made a one-off error under pressure.

"Since this matter arose, I have been taking precautions with importing; testing randomly and also requiring Sweet Romance to forward the signed documents from their platers, confirming they have not used nickel in any of the plating."

She added she would, in the future, be more proactive in checking the details of anything she published or announced, such as a sign stating products were nickel-free.

The case was adjourned until next month, to allow pre-sentence reports to be prepared.

Magistrate Theresa Dickson told McEwan she could expect to receive a medium community sentence.