The pair, whose real names are Nicola and Rosie Dempsey, do have some fans. The pair have been described as Marmite due to their ability to attract love and hate, the Daily Mail reported.
One user, Tyler Brogan wrote: "Love the Crimbo advert, so catchy."
Emma Scott added: "Awesome work."
Ross Fotheringham said: "Well done Nationwide. This is excellent."
Nationwide's Chief Marketing officer Sara Bennison told Ok! Online: "When we saw an audition tape for Flo & Joan, gut feel told us all that they were a delightfully fresh take on things like loyalty which are at the heart of Nationwide.
"Social media has provided a great instant barometer of reaction - good and bad. The huge amount of likes and shares have been great.
"But then there are others who have chosen to post the most vile, abusive and misogynistic comments about the duo. It is not just our Flo & Joan adverts that generate these comments, it is also our adverts that feature people of different colours, backgrounds and perceived sexuality, which attract the most criticism.
"That's why it is important to call out those persistent offenders who put out vile comments on a regular basis and who should really know better.
"That is why Nationwide is looking to work with other brands, industry bodies, such as ISBA, and the Met Police to look at the true scale of this worrying trend to spread hate from behind a keyboard and attempt to create a solution to tackle the issue.
"It's one thing not to like an advert, another to threaten to kill the stars of it. Abuse is abuse and that's never OK in our book."
In real life Flo and Joan are British sisters Nicola and Rose Dempsey.
They are veterans of the Edinburgh Festival, have performed with success in North America and their 2016 Song became a massive online hit, attracting 46million views across social media.
Their piano-and-percussion act has been compared to Flight Of The Conchords and Flanders and Swann.
