Sienna Miller gave short shrift to the recent rumours that she and fellow celebrity divorcee Brad Pitt are dating, describing the reports as “silly”.

The 35 year old actress, who divorced her ex-husband Tom Sturridge in 2015, spoke to Page Six at a Cinema Society screening of her latest film The Lost City of Z on Tuesday night (April 11th).

Brad PittBrad Pitt's production company was involved in 'The Lost City of Z'

Pitt’s production company Plan B is behind the movie, and he and Miller were reported to have been “heavily enjoying each other’s company” and “talking to each other all night” at a dinner for the film the previous evening by the same publication. Another source had suggested that Pitt was “in very high spirits, which he hasn’t been for a long time. He seems to be over a hump.”

Asked about it, Miller laughed off the suggestion. “I’m not going to even dignify it with a response. It’s predictable and silly,” she said frankly.

More: Sienna Miller recalls filming an entire DAY of sex scenes with Ben Affleck

Many reports about 53 year old Pitt, who is in the middle of a complex divorce and child custody battle with his estranged wife, Angelina Jolie, since their divorce was announced back in September last year, have centred around his apparent dramatic weight loss, and concerns that his health might have gone downhill since his separation.

Sienna MillerSienna Miller is one of the stars of 'The Lost City of Z'

However, his gaunt figure is apparently down to a weight-loss competition between Pitt and Miller’s co-stars Robert Pattinson and Charlie Hunnam for their roles in The Lost City of Z, a film about British explorer Percy Fawcett’s search for a mysterious city in the Amazon in the 1920s.

“It became funny… almost like a bizarre competition,” the director James Gray in a recent interview. “It would be like, ‘You’ve got a pear in your lunch, and I just got water.’ It was who could lose more weight, who could torture themselves more.”

More: Brad Pitt smiles as he joins ‘The Lost City of Z’ cast at L.A. premiere [pictures]