"Isn't It Romantic" co-stars Liam Hemsworth and Rebel Wilson have been sued for sharing paparazzi photographs on their Instagram accounts.

According to Splash News, Hemsworth claimed in a California federal court that he infringed its rights in a behind-the-scenes photograph of him on the film's set that it licensed to The Daily Mail last year.

The photograph was posted on Hemsworth's Instagram feed in July 2018 and in June 2019, the first post promoting the film itself and then encouraging fans to vote for it in the Teen Choice awards, reports hollywoodreporter.com.

"Legitimate publications to which Splash looks to pay syndication fees are unwilling to pay for work that is already widely disseminated on the Internet for free by pirate sites and well known celebrities," stated attorney Peter Perkowski in the complaint.

Perkowski also argued that Hemsworth's over 13 million Instagram followers would have been interested in seeing the image in magazines that paid to license it.

Splash said the infringement was wilful and therefore Hemsworth should pay statutory damages of up to $150,000 for each unauthorised use -- plus another $25,000 for removing the watermark.

The same lawyer on the same day in the same court sued Wilson on behalf of Xposure Photo Agency. Wilson is being sued over photographs from the set of "The Hustle" that were posted on her Instagram and Twitter accounts in April 2018.

Xposure argued that the behind-the-scenes nature of the pictures makes them valuable -- unless the star's millions of fans see them on social media. This suit seeks the same statutory damages for alleged wilful infringement and watermark removal.