Hollywood star Daniel Radcliffe acted like an "absolute d**k" during a crucial 'Harry Potter' kissing scene.

The actor has offered an apology to his castmates Emma Watson, and Rupert Grint after the movie star confessed he wasn't on his best behaviour when the pair were called on set to film a smooch between their characters Hermione Granger and Ron Weasley for 'Harry Potter and the Deathly Hallows: Part II', reports aceshowbiz.com.

Speaking in HBO special 'Harry Potter 20th Anniversary: Return to Hogwarts', the 33-year-old explained: "I did not make this (awkward situation) better, because I've been told significantly that I was just being an absolute d**k about this and was like, 'I'm gonna come on set and watch you guys kiss. I'm sorry about that, guys.'"

During the reunion show, Emma revealed she felt uncomfortable kissing Rupert because he felt like a brother to her after they all grew up working on the films together.

She said, "Obviously us kissing was the most horrifying thing either of us have ever had to go through ... (It) felt wrong ... Everyone wanted to be on set for it. Cause everyone was like: 'This is gonna be good, guys.'"

She also opened up about having a crush on her co-star Tom Felton, who played Draco Malfoy in the wizard movie series and was three years older than her.

Emma recalled: "I walked into the room where we were having tutoring. The assignment that had been given was to draw what you thought God looked like, and Tom had drawn a girl with a backward cap on a skateboard."

"And I just don't know how to say it - I just fell in love with him. I used to come in every day and look for his number on the call sheet, it was number seven, and if his name was on the call sheet, it was an extra exciting day," she continued.