Employer refusing to pay pending salary after resignation?

I recently resigned from my job at a tech company in Bengaluru. I served the full notice period of 1 month as per my contract. However, my employer is now refusing to pay the pending salary for that month, citing vague performance issues. This has left me financially strained and I'm not sure how to proceed. Can I take legal action to recover my dues? What steps should I take to resolve this matter?