Speculation mounted that the ''That 70's Show'' co-stars had taken their friendship to the next level after they were spotted shopping for furniture together and taking a three-day mini-break in California.
However Mila, 28, considers reports she is dating the ''Two and a Half Men'' actor to be ridiculous.
She told US show ''Extra'': ''It's very absurd. I've never commented on my personal life - I'm not going to start commenting on my personal life now. But it's a friend. A friend is a friend.''
However, sources claim Ashton, 33 - who split with wife Demi Moore after six-years of marriage last year amid allegations he cheated - used to have a huge crush on her.
The insider told: ''He was so in love with her for a while when they worked together. He thought she was a goddess, was always talking about how beautiful she is. But she was with Macaulay [Culkin] for a lot of that time and also just generally gave off a not interested vibe.''