I posted on this before and meant to come back sooner but been having a busy day with NB DD. I mentioned I worked in ethical fashion and wanted to share more tips in case anyone is interested...
Already mentioned that organic standards have virtually the same 'people/worker' standards as Fairtrade certification so shop organic where possible. Watch out for Primark's ethically/sustainably sourced cotton -this is not the same and I often find it's mixed with other fabrications and is harder to recycle later, so part of its content is sustainable but it's not sustainable in the future. If you're worried about the volume of fast fashion that's so cheap and poor quality being dumped in landfill (because 8/10 items sent to charity shops end up in landfill) then shop 100% natural fibre products eg 100% cotton, so at least the fabric can be recycled in some way. Fabric made with man-made fibres mixed with other fibres can't be recycled other than sold as second hand. Even shopping '100% polyester' is better than mixed fabrications because if the clothing is worn out, the fabric can still be recycled.
However, I've recently stopped buying clothing in man-made fibres altogether because it's not breathable and makes me hotter/sweaty...TMI?? 
If you have the time, watch The True Cost, a film on fast fashion. My boss was featured in the film and we met the filmmaker, who wanted to highlight the bad practices within the industry, from factories poisoning villages by disposing of clothing dyes unethically/illegally in the local drinking water, factory workers' rights, the Bangladesh factory fires and to huge corporations such as Monsanto leading cotton farmers to commit suicide because of huge debts. Rather than avoid Primark, avoid evil genetically modified product companies like Monsanto... the film explains all.
Sorry, bit of a long post but I'm passionate about it. Watch the film... the ending made me cry when you see a montage of shots...from the greed of shoppers racing in to shop the Black Friday sale to the loneliness of the factory workers who leave their children in the countryside to work in Dhaka and provide for their children.