Sales of Fairtrade products were up 44% last year, according to data produced exclusively for The Grocer ahead of Fairtrade Fortnight, which kicks off on Monday.

TNS Worldpanel figures show sales hit £225m in the year to 4 November 2007, with 63% of British households buying at least one Fairtrade product.

Fruit was the category's best performer with sales reaching £108m, 88% more than the previous year. The switch by Sainsbury's and The Co-operative Group to sell only Fairtrade bananas was the main driver of this.

Sainsbury's change of policy also helped it to become the UK's biggest retailer of Fairtrade products. With almost 30% of the market, it overtraded in the category by 97%. The Co-op Group was the second biggest Fairtrade retailer with 18% of the market, ahead of Tesco's 15%. Sainsbury's and The Co-op's Fairtrade own-label ranges were also the first and second bestselling Fairtrade ranges as Fairtrade pioneers such as Cafédirect and Clipper Tea were eclipsed by own label in the rankings. Cafédirect, last year's top-selling Fairtrade brand, fell to 6th, while Clipper, 6th last year, dropped to 9th.

However, the success of own label has prompted concern about downward price pressure. A Fairtrade jar of branded instant coffee sells for about £2.50 now, 50p less than a year or so ago. Promotional activity was "undermining what the Fairtrade mark is about", said one brand owner.

But retailers said they simply wanted to challenge the idea the category was expensive. "I'm happy to see the price per item falling," said Brad Hill, Co-operative Group Fairtrade development manager. "The important thing is to continue driving volume while the promotions create long-term gains."

The Co-op Group will be offering 20% off many lines during Fairtrade Fortnight.

The Fairtrade mark, meanwhile, is facing rising competition from other ethical logos, such as Rainforest Alliance and Utz