A digital marketing company has apologised after advising the creators of YouTube videos to include the word "Holocaust" in titles to increase the number of viewers.

Vidooley said it was a “great time to release videos related” to Holocaust Memorial Day on January 27.

In what appeared to be an email to clients, it suggested ideas for videos such as “5 Holocaust movies you must watch”, "Holocaust timeline explained for dummies" and “10 Holocaust stories you will NOT believe”.

The American-based company, which describes itself as "a YouTube audience development and analytics suite", pointed out that Holocaust was searched as a keyword by YouTube viewers 200,000 times a months.

The email was posted by several Twitter users, with one writing it was “incredibly insensitive” to try “to turn the Holocaust into clickbait”.

In response to the criticism, the company said it apologised "to every member of the Jewish community for hurting your feelings. We’re really sorry".

It added: "Our only intention was to showcase how a YouTuber should make videos about important socio political or cultural events to keep their audience informed and engaged. We didn’t necessarily want them to use click-bait titles to increase their viewership, but the examples used in the email were wrong."