The mutual has acquired the Egg brand, as well as the £4bn mortgage and savings book, for an undisclosed sum.
A spokeswoman for Yorkshire did not rule out putting an end to the Egg brand, adding it was “it was too early to say” whether it would go or stay.
The sale of the accounts comes four months after Barclaycard bought the Egg branded credit card business from. Egg will disappear as a credit card brand by the end of the year when customers will switch to Barclaycard.
Citi has now sold all of Egg’s assets it bought from Prudential for £575m in 2007.
The latest deal comes as it emerges that Patrick Muir, founding marketing director of the Egg brand, has left his position as chief marketing officer for Citi’s consumer business in the UK. It is not clear if he has a job to go to.