AceShowbiz - Ewan McGregor's daughter Clara regrets her angry reaction to her dad's affair with his Fargo co-star Mary Elizabeth Winstead.

Last year (17), Clara's mum Eve Mavrakis announced she and Ewan were separating after 22 years of marriage, after the Trainspotting actor was spotted kissing his castmate in a London cafe.

Clara, who made headlines in July when she branded Mary a "piece of trash" on Instagram, now admits she went around her parents' split the wrong way.

"It wasn't the most mature way to go about things, but I was angry and upset" she told British newspaper The Times. "There had been a lot building up to it and a lot to deal with - but yeah, it wasn't my finest moment."

Explaining the reasons behind her Instagram outburst, the 22-year-old model and aspiring actress added: "I kept being tagged in this photograph (of Mary) and I was seeing negative things about my mom. I said how I felt and I didn't want to apologise for it. It wasn't the right way to go about things, but it's a hard thing to wrap your head around when you had this idea of what the family unit is and then to have that shift. It's very weird."

And it wasn't just her dad's lover that received a tongue-lashing.

"I dealt with stuff with my dad personally - it wasn't just me letting it slide with him and just getting mad at her. Of course not," she clarified.

Although she knew her mum and dad's marriage was on the rocks when the photograph of Ewan and Mary was published, Clara was upset with the pair for being careless about going out in public.

"The picture surfaced on my sister's birthday, but my dad didn't know it was going to come out," she sighed. "He didn't want us to see that, but you know, there were paparazzi following them around."

Ewan also has daughters Jamyan, 17, Esther, 16, and seven-year-old Anouk with Eve.