Sainsbury’s has vowed to covert all its TU t-shirts to ethically sourced fair-trade cotton by January next year.

The cost of t-shirts will remain at£3, with Sainsbury’s absorbing the extra£1 million costs associated with the move. This figure would equate to about 1.8 million garments.

Sainsbury's retail director Ken McMeikan said: “It is no longer a case of choosing between ethical and value. We must be both ethical and affordable.”

In a second-quarter financial statement released yesterday, the group also announced that its entire range of own-brand tea will become 100 per cent fair-trade over the next three years. This will make Sainsbury’s the UK’s biggest fair-trade tea retailer and triple fair-trade tea sales in the UK.

The move follows the supermarket's much-publicised shift to selling only fair-trade bananas earlier this year.

Speaking at an industry convention, McMeikan said the ethical consumer was becoming more mainstream and increasingly women were the driving force behind this shift in behaviour.

He added that the consumer was looking to the supermarkets to make these changes and trusted them to do so more than governmental bodies.

Meanwhile, leading retailers including Marks & Spencer, Sainsbury’s, Debenhams, Topshop, the Co-op and Waitrose attended the Fairtrade Foundation’s annual autumn conference to mark the start of the build-up to Fairtrade Fortnight 2008, which will take place between February 25 to March 9. The theme for the fortnight was announced as: Change Today. Choose Fairtrade.

Fairtrade Fortnight 2007 helped nearly double retail sales of products carrying the Fairtrade mark over the two week period.