Dear Dr. Shu,
The problems of this kind arise because HR professionals in general and top leadership, in particular, do not understand the difference between the removal of employees on account of "administrative reasons" and on "disciplinary grounds".
Underperformance is not an evil act as such. Yes, your previous employer had certain expectations for your position and since you could not meet those expectations, they removed you. Removal from the job is nothing but a punishment. Therefore, explain to your employer that for whatever happened in the previous company, you have already been punished. If the current employer also takes action for what occurred in the previous employment, it would be double punishment and against Indian jurisprudence. Principles of natural justice enshrined in the constitution do not allow more than one punishment, even for a crime.
Address your letter to the MD of the company. However, route it through the HR department.
General Comments: The post reflects the psyche of Indians in general. People always expect everyone to succeed every time, and failure is considered morally bad or wrong. It is believed that those who fail once will fail forever. This is nothing but social bias. The sooner HR professionals get rid of it, the better for society.
Thanks,
Dinesh Divekar