German discounters Lidl and Aldi's share of the grocery market has jumped to 8.5%, its highest ever, as Irish customers begin to shop around. Aldi has seen sales growth of 20% in the last quarter, while Lidl has achieved growth of 10% in the same period, according to market research from TNS Worldpanel.

New shops and more promotions have helped drive their sales, despite the fact that the value of the grocery market in Ireland overall has started to shrink as prices fall.

The discounters are winning market share from all of their rivals. Tesco's market share is now 25.6%, Dunnes' is 23.6%, SuperValu's is 20.5% and Superquinn's is 7%.

More people are visiting each supermarket to take advantage of price promotions, and as a result, the average spend per customer per visit is down.

Cross-border shopping remains popular but there has been some decline since Tesco, in particular, started cutting prices, suggesting its 'Change for Good' campaign is having an effect. Tesco started the campaign after like-for-like sales in its operations in the Republic fell "well below expectations", it said in a circular to suppliers.

"Consumers, media and government associate Tesco Ireland almost exclusively with price differentials between Northern Ireland and Ireland. Having invested circa stg£3bn in Ireland, the damage to the Tesco Ireland brand by our almost exclusive association with the retail premium versus Northern Ireland is unacceptable," said the document, circulated by Tesco head office in Britain.

Sainsbury and Asda's share of the market in the Republic has fallen from 2.9% for the three months ending 17 May to 2.6% for the three months ending 12 July.