Sienna Miller finds suggestions she dumped Jude Law for a co-star "laughable".

The 29-year-old actress -- who called time on her 13-month relationship with the "Alfie" star in January -- insists the split was "amicable and mutual", and slammed recent rumours she is dating Joe Armstrong, who she stars with in London stage production "Flare Path," as "ridiculous".

She said: "I'm single! Poor Joe is like, 'What's going on?' We all find it ridiculous and laughable. I do feel very picked apart by it.

"When two people have separated and have both stated that it's amicable and mutual yet, regardless of that. It's not a nice feeling to have people talk about you behind your back and for it not to be true and for you not to be able to retaliate."

However, the "Edge of Love" star -- who first dumped Jude in July 2005 after it was revealed he has been having an affair with his children's nanny Daisy Wright - admitted it is "human instinct" to be selfish in relationships.

Sienna added to Time Out magazine: "I think there's a human instinct to be selfish, especially in matters of the heart."