Mary Elizabeth Winstead's ex-husband Riley Stearns has denied sending death threats to actor Ewan McGregor.

Film director and TV writer had seemingly become incensed after the pair went public with their controversial new romance and allegedly told the A-list actor he was "f***ing dead" in a furious rant on Instagram.

The now deleted post read: "Call me a cuck, will ya? Laugh at me, will ya? "F*** the woman of my dreams behind my back, will ya? @mewins @mscregor_ewan You're F***ING dead..."

Stearns has since denied writing the menacing message in an Instagram story, saying it was photoshopped. "It is so stupid that I have to actually post this but the British tabloids have published a photoshopped Instagram post as if it was something I wrote.

"This whole process has been a lot for me but to have people out there actually think I wish harm on my ex-wife makes me sad," he added.

Winstead left him in May but there is no proof of infidelity.

It is important to note that while the account - followed by 6,747 people - features intimate home pictures of the actress from their marriage, there is no way to authenticate the post.

Earlier in November, the Fargo co-stars were seen hand-in-hand in Hollywood, days after photos of the two kissing at a restaurant in London surfaced online.

McGregor's estranged wife Eve Mavrakis, who he married in 1995 and shares four children with was said to be "heartbroken" after learning about her husband's relationship with Winstead.

The product designer opened up about her marriage woes when a fan sent her a message on Instagram which read: "I can't believe Ewan would end things with u for that cheap xxxxx! U are so much better than him!!!! Take him for every penny u can!!!!"

She simply replied, "What Can I Do?"