The number of people travelling across the border to buy their groceries has increased by nearly 31% in just one year.

Research from TNS Worldpanel shows that 122,000 households in the Republic of Ireland shopped in either Sainsbury's or Asda in the quarter ending August 2008, representing 8% of total households, compared to 6.2% in the same quarter in 2007 when 93,000 householders shopped there.

"It will be interesting to see this trend over the Christmas period," said TNS Worldpanel's managing director Marie Burke. She suggested that the Ikea factor could be at play, with householders stopping in grocery shops on their way home from a visit to the Swedish furniture giant.

The research found that 25 identical stock-keeping units in August were 33% more expensive in the Republic than in Northern Ireland. That was down from a 48% difference in April.

Burke said it was worth bearing in mind that "the exchange rate accounts for a lot of this difference but this is the difference in price the shopper paid".

Several British retailers are known to be interested in entering Ireland. Wal-Mart-owned Asda has been scouting sites here and has had talks with developer Treasury Holdings about opening on sites the property company owns at Balgaddy in west Dublin and near Leixlip in Co Kildare.

Sainsbury's, meanwhile, has been linked with a bid for Superquinn, which for the year ending 10 August 2008 had a 7.7% share of the Irish grocery market, down from 8.1% the previous year, according to TNS Worldpanel.

In addition, Waitrose owner John Lewis is planning to open anchor fashion shops at Dundrum and O'Connell Street in Dublin and has also had talks about opening at Liffey Valley, leading to speculation that it may look to bring its grocery arm here.

One of the attractions of Superquinn for any potential purchaser, according to retail sources, is the fact that it already has a central distribution centre, meaning next-day delivery for any goods ordered by its shops. This is important for retailers as it increases the shelf life of products, reducing waste.