Gwyneth Paltrow is reportedly not impressed with Scarlett Johansson’s behaviour on the set of their new film Iron Man 2.

In the film, Gwyneth returns to her role of Pepper Potts, assistant to Robert Downey Jnr’s Tony Stark, while Scarlett has a guest role in the sequel as super-spy Natasha Romanoff/the Black Widow.

An on-set source told the Sun: “Gwyneth has become very frustrated with Scarlett.

“They come from different worlds and have completely different styles.

“Gwyneth was looking forward to working with Emily Blunt, who was originally in line for the part, but it ended up being Scarlett.

“Gwyneth’s had to live with that and she has been very professional, but she and Scarlett haven’t developed a friendship on the shoot, which is almost at the half way point. In fact, it’s quite the opposite.

“Gwyneth has found Scarlett very demanding of the attention of the crew. It’s not a happy set.”

Filming began in California last month and is expected to wrap over the summer. The film is set for release in May 2010.