Last week was a momentous one for the Fairtrade movement and not just because it marked the start of Fairtrade Fortnight. Tate & Lyle's announcement that it would be switching its entire retail cane sugar range to Fairtrade within two years marks the single-biggest shift to the mark to date. So has a logo that was once regarded as the preserve of niche health products reached tipping point?

Fairtrade has undoubtedly become more mainstream since Sainsbury's and Waitrose switched all their bananas to the mark in 2006. But nothing comes close to the scale of Tate & Lyle's move.

Its commitment will increase tenfold the total volume of Fairtrade sugar sold in the UK in 2007 and will generate Fairtrade premiums of about £2m for small-scale growers in Belize, says marketing director Steven Hermiston in an exclusive interview with The Grocer.

"We are leading the way. No-one else has done anything like this on this scale," he says. "We are a big supporter of Fairtrade and would be very pleased if other manufacturers followed suit."

He is quick to dismiss allegations that the move is a cynical marketing ploy. The motivation behind the adoption of the logo, he says, is simply that consumers want it. Consumers are becoming more concerned about ethical shopping and the Fairtrade logo helps a company to "communicate its ethical credentials", he says.

His assertion is certainly backed up by the statistics. Over the past couple of years, consumer demand has risen sharply. TNS Worldpanel data reveals about 63% of British households bought Fairtrade in the year to 4 November 2007, representing an increase of four million households over the previous 12 months. According to the Fairtrade Foundation there was an 81% increase (to £493m ) in sales of Fairtrade products in 2007.

It's a no-brainer for companies to adopt the mark, believes Mark Varney, business development manager for the Fairtrade Foundation. Not only does it improve their corporate social responsibility credentials, it also allows them to tap into an obviously lucrative revenue stream.

"For the growers, we are a certification body that helps alleviate poverty through trade, for the consumer the Fairtrade mark allows them to engage with the product and gives them an idea of its provenance and for businesses it is a good marketing tool to facilitate dialogue with customers," he adds.

As well as growing the share of categories Fairtrade operates in - such as bananas, cocoa and coffee - there is huge potential for growth in untapped areas such as soya and pulses, he suggests.

There are challenges, Varney adds: "We are already in dialogue with lots of organisations, big manufacturers and brand owners but it is important for the credibility of the mark itself that we move forward in a committed and credible way," he says.

Hermiston warns: "The two major barriers manufacturers must overcome if they want to switch to Fairtrade are availability issues for a mass market and the thorny question of price premiums," he says.

Tate & Lyle is already contemplating switching its ingredients arm, he reveals, but this would take longer than the retail arm.

Fairtrade's growing ubiquity will inevitably attract allegations of "greenwash", but with consumer demand for ethical labels showing no sign of waning, more retailers and manufacturers will no doubt take the view that there's more to gain than lose by making the switch.