Gillian Anderson's biggest fashion regret is spending ''an awful lot of money on clothes''.

The 'X-Files' star admits one of her fashion faux pas was dropping $1,400 on a dress she never wore when she was younger and she was ''filled with shame'' by it.

She said: ''I've spent an awful lot of money on clothes. It's one of my big regrets. I cannot believe that I was so reckless to spend $1,400 on a dress that I never wore in my twenties. I was making a lot of money and had a boyfriend who was a model. He introduced me to stores I'd never heard of in Los Angeles. So, I got used to trying stuff on and not really looking at the price tag. I cannot believe I did that; I'm filled with shame.''

And Gillian doesn't think she's dressed in ''anything quite as offensive'' since her first gold Golden Globes gown.

She added: ''I have looked in the papers the next day and thought, Well, that was a mistake. But the regret doesn't last. Many years ago, for my first Golden Globes outing, I made a fashion choice that I cannot quite understand now ... It was a gold dress, slightly like a geisha style, with a band around the middle. I was on the worst-dressed lists all over the world. I don't think I've worn anything quite as offensive since then.''

The 51-year-old actress believes moderation is ''key'' when it comes to fashion.

She told Elle magazine: ''The best fashion advice? Keep it simple. Moderation is key. That's what fashion has taught me about life. Moderation in terms of price of purchase, accessorising, the style of pieces you're wearing, whether it's a dress or separates. Nothing over the top - it's too much information. Classic, usually single colours; not frilly or patterned.''