Charlotte Todd stands next to the dress she designed, and which was worn by Kate Middleton before it was auctioned for $150,000.(AP Photo/Alastair Grant)

A revealing dress worn by Kate Middleton at a 2002 charity event attended by Prince William when they were university students has sold for £65,000 ($NZ150,000) at auction.

The black see-through dress with a blue trim was bought by an unidentified buyer today in London. The auction price, which excludes a 20 percent buyers' premium, was originally expected to reach £8000.

Some commentators maintain that the dress played a role in sparking the royal romance that started shortly after the event.

It was initially intended to be worn as a skirt, but Middleton wore it as a short dress with black lingerie underneath.