The UK imported 113,000 tonnes of Cheddar between January and October 2008, up 30% year-on-year, according to DairyCo. Some 87,000 tonnes of that - almost 30,000 tonnes more than in 2007 - came from the Republic of Ireland.
Lower milk production meant UK manufacturers were more likely to put their milk into premium cheeses, said DairyCo head of market intelligence, Huw Thomas.
"We are losing milk supply in Britain, so there's not so much commodity Cheddar around," he said. "But premium lines are a good direction."
On the other hand, Irish producers, which could switch relatively quickly between commodities, had increased Cheddar production following the collapse of global wholesale milk powder prices, he said.
Although rising import costs could hit import volumes this year, in 2008 an increasing number of manufacturers bought cheaper Cheddar from abroad in a bid to cut costs, added a UK industry source.
"There's always been a large market for imported Cheddar in this country," he said. "Much of this goes into lower tiers such as foodservice where provenance and quality are less important."
Most of the major multiples were still using British suppliers for their own-label Cheddar, but Tesco was sourcing the majority of its Value cheese from Ireland, the source said.
Last week the NFU called on retailers to increase the number of British cheeses they offered across basic, standard and higher-tier categories.
With the volume of higher-value lines being produced in the UK rising, less speciality cheese is already being bought from abroad.
Some 229,000 tonnes of speciality products were imported between January and October compared with 258,000 tonnes in the same period in 2007.