Actress Blake Lively has apologised for an “awkward, sort of clumsy” photoshop fail, mocking Princess Kate’s edited Mother’s Day photo, according to News Corp columnist Louise Roberts.

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

The actress mocked Princess Catherine in an Instagram post that poked fun at her photoshop fail earlier this month.

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

“I find it staggering that these celebrities would even engage in this sort of insult and this sort of terrible behaviour towards a woman who was already unwell,” Ms Roberts told Sky News host Caroline Di Russo.