Sales of Dairy Crest's Country Life, which ran a high-profile ad campaign fronted by former Sex Pistol John Lydon , pulled clear of Arla's Anchor for the first time last month.
Country Life's value share of the butter category has reached 7.6% against Anchor's 7.1% [Nielsen 4w/e 8 August 2009].
The Country Life brand is worth £63m annually, with value up 13% and volume up 18% in the year to 8 August, closing the gap on Anchor's £88.7m.
"The Country Life campaign has been successful in meeting all our core objectives," said Dairy Crest marketing director Paul Fraser.
However, Arla senior brand manager Mike Walker claimed heavyweight promotional activity had been central to the surge in Country Life sales, pointing out that 72.9% of Country Life had been sold on promotion during the period.
"Unless its strategy is to continue selling 75% of volume on deal, Anchor does not think Country Life's success will continue," he added.
Dairy Crest has announced it will run British-themed idents during its sponsorship of the new Blighty TV channel.