The price war between the big two of the Irish grocery sector, Tesco and Dunnes Stores, has spilled over into the courts.

Tesco took exception to 'price comparison' ads being run by its rival in the Irish national newspapers and headed for the Dublin High Court. The company's counsel, Ciaran Lewis, cited three ads in which, he said, Dunnes was "not fairly comparing prices" and was in breach of consumer protection legislation.

Tesco had previously written to its rival asking that the ads be discontinued, he said, "but the correspondence has been ignored". Tesco asked for and was granted an injunction to prevent the ads being run again while the case was being heard.

Counsel for Dunnes, Declan McGrath, claimed the Tesco case was "misconceived in law, as it has engaged in advertising similar to that about which it is now complaining".

The legal skirmish has been adjourned again while the price war goes on.

In recent radio and newspaper ads, both companies have made comparisons between their prices. Dunnes plays the patriotic card with its 'home team' slogan, "the difference is we're Irish", while market leader Tesco responds with "we're cheaper".

The intensity of the battle has been heightened by the recession and the cross-border exodus.

Latest Bord Bia figures show the value of the Republic's grocery market has fallen 2% in the past 12 months to 9.13bn.