I am currently working in a bank as an administrative staff. I am aware that as a bank employee, I receive salaries which are most probably coming from the bank's interest based income. I feel uncomfortable with this and I am currently seeking for a better job. What I want to ask is regarding my earnings? Can I use them during my time in the bank, or is it all unlawful?
You need to figure out approximately how much part of your salary comes from interest based income and get rid of that amount. Because Allah sets “cleanliness” as a condition to spend our earnings. He commands:
“Believers! Spend clean things from what you have earned and from what We have produced for you out of the earth. (…)” (2:267)
So you can use the remaining part of your salary while you look for other jobs.
Working in a bank can only be permitted on the condition that you look for other jobs, and be in a struggle for changing your job as soon as possible.