In light of Princess Catherine's announcement over the weekend that she was diagnosed with cancer, actress Blake Lively has apologised to the Princess of Wales over a now-deleted social media post.

The actress mocked Princess Catherine in a now-deleted Instagram post that poked fun at her photoshop incident earlier this month.

Ms Lively said she felt “mortified” by the post following revelations that the Princess was undergoing preventative cancer treatment.

“I made a silly post around the ‘photoshop fails’ frenzy, and oh man, that post has me mortified today,” Ms Lively wrote on her Instagram story.

The Daily Mirror’s Royal Editor Russell Myers reacted to Lively's apology, saying she is “very much eating humble pie this week after she was caught out mocking the Princess of Wales over her photoshop fail”.