The English designer Katharine Hamnett, 60, is best known for her power-dressing collections and political T-shirts of the 1980s. Indeed, she considers herself as much a campaigner as a designer. She has collaborated with the Environmental Justice Foundation to highlight the ethical problems of the global cotton industry. For autumn/winter 2008-09 she will reissue her classic 1980s slogan prints.

You'd have to be a psychopath not to acknowledge other designers. I love Alexander McQueen and Vivienne Westwood.

Wearing clothes is all in your bearings. I was locked out of a hotel room naked once but managed to pull off the corridor carpet and wrapped it around me as a dress - then I went down to reception. It is about how you stand - you can get away with anything.

When I was growing up, there was a great deal of fashion competition in my family. My mother and her siblings had hat wars, shoe wars and handbag wars. We moved to France when I was 5, and that was another kick up the ass in a style sense. Being at the French lycée meant that my lovely girlfriends, who were all daughters of Arabian ambassadors, would come to school in Courrèges (ultra modern French designer). It was horrendous competition. The memorable thing for me is that I actually survived sartorially in that extremely ferocious spotlight.

After college, I started doing what most art students do: I made science-fiction clothes and thought that they were going to take the world by storm. I had a label with a friend and we worked 16-hour days, seven days a week for three years. We were doing everything from deciding on the designs to making the designs, setting patterns, making samples, taking orders and doing the manufacturing on my old sewing machine from home. Suddenly I thought: “F*** this.” It was just too hard. I needed to do something more commercial. So I did a collection of black leather separates that were actually quite erotic. Joseph took them on a sale-or-return basis, but they flew out of the shop in seconds. That was the start of the Katharine Hamnett brand.

I wasn't surprised by the success. I have always been terribly pigheaded. The 1980s completely took off for us, and it was total lunacy. But the success was actually a bit yuck. I am not crazy about the whole fame thing, but it was great to have financial security. We had an unbelievable amount of PR, to the point where it was nauseating. A woman at French Vogue, for example, thought the elastic bands I'd just shoved around my wrist were a chic fashion statement. It was bizarre.

We had been invited to meet Margaret Thatcher but, to be honest, I didn't want to go. I thought she was dreadful. The way she was acting was appalling and what she had done to the country was deeply bad. As Jasper Conran said to me the day before our meeting: “Why should we go for a glass of warm white wine with that murderess?” - which is one of the greatest lines ever. Then I thought: “This is an obvious photo opportunity so I'll take advantage of it.” That is why I wore the anti-Pershing T-shirt. I kept it hidden under my jacket, but when I shook hands with her I got it out on display. She didn't notice it at first, but then she looked down and made a noise like a chicken, then quick as a fishwife she said: “Oh well we haven't got Pershing here, so maybe you are at the wrong party”, which I thought was rather rude as she had invited me. The Imperial War Museum wants the T-shirt, but I am hanging on to it.

Some 20,000 farmers die each year in the developing world from accidental pesticide poisoning. I went to Malé [the capital of the Maldives], and saw mothers who had lost their children through farming [accidents] and people who were living in conditions worse than most animals endure. It's just unimaginable. In the West we have got this spoilt attitude - we're obsessed with celebrities and not concerned with the people who actually make our clothes. So I thought that I must use my influence to change people's perceptions.Until now, we had been fighting a losing battle. Nobody wanted to know about fashion and ethics 20 years ago. But we carried on dealing with things that were regarded as taboo. Back in the 1980s American Vogue finally came to our offices in North London, as we were doing incredibly well on every level. They walked in, saw the statement T-shirts about world peace and banning nuclear weapons and without a word spun on their heels and walked straight out again.

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