Reese Witherspoon and Vince Vaughn may be in for a rocky ride promoting their new movie - because the pair reportedly can't stand each other in real life.

Rumours that the pair don't exactly see eye-to-eye first surfaced earlier this year, when it was claimed that their furious bust-ups threatened to halt filming on Four Christmases.

And it doesn't sound as if they've grown on each other since then.

A friend tells OK! that Reese has said Vince is, “the biggest child I've ever met!"

The friend adds, “Promoting a movie involves long hours, and she’ll have to spend a lot of time with someone who gets under her skin.

“Reese is professional — she’ll grit her teeth, fake a smile and pose for pictures — but she’s not looking forward to it.”

Reese herself has confessed she was definitely not on the same page as Vince during shooting.

She said, “I said to him one day, ‘People can’t talk as fast as you think.’ You can’t keep up with him. But I feel like I’ve been in training — Vince Vaughn training!”