Right-wing tabloid slammed for using racist dog whistle in story about Prince Harry marrying biracial actress
Prince Harry and fiance Meghan Markle (Screen cap).

A right-wing tabloid in the United Kingdom is facing criticism after publishing a headline describing writer Sarah Vine's "niggling worry" about Prince Harry marrying biracial actress Meghan Markle.

"Yes, they joyfully in love," reads the headline of Vine's front-page story in the Daily Mail. "So why do I have a niggling worry about this engagement picture?"

The word "niggling" in and of itself is not racist, as it's defined as a persistent discomfort or concern. However, it is also very close to the word "nigling," a slur used by white supremacists to disparage black children.

Given that headline writers are often very careful and deliberate in the words they choose -- especially if those words could provoke strong reactions, and thus help sell more papers -- some critics believe that the Daily Mail intentionally used the word "niggling" as a racist dog whistle.

Check out some reactions from UK Twitter users below.