Answer
(Fatwa: 46/47=L)
It is narrated in Hadith:
عن جابر رضی اللہ عنہ قال: لعن رسول اللہ صلی اللہ علیہ وسلم آکل الربوا و موکلہ وکاتبہ و شاھدیہ وقال ھو سواء (مشکوۃ 1/244)
The Prophet (peace be upon him) accursed one who devours usury, one who feeds it, one who writes it and one who bears witness to it. He added: They all are equal. (Mishkat: 1/244)
Therefore, doing a work in bank which involves giving interest-based loan to people is unlawful. But, you are not asked the leave the job immediately, it is advised to look for a lawful job and when find one leave the bank.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband