What is mala fides?
“Mala fides or bad faith” means dishonest intention or corrupt motive in the exercise of powers or a deliberately malicious or fraudulent purpose, on the part of the decision maker. Mala fides includes those cases where the motive force behind an action is personal animosity, spite, vengeance, personal gratification or benefit to the concerned authority or its friends or relatives. (Halsbury’s Laws of India, Vol-1, P.319 and CS Rowjee V. A.P., AIR 1964 SC 962).
An independent ground of attack, malafides (Malice in fact) should be distinguished from mala fides (malice in law). According to Megaw LJ, it always involves a grave charge and it must not be treated as a synonym for an honest mistake. (District Council V. Kelly, (1978) 1 All ER 152). There is malice in law where “it is an act done wrongfully and willfully without reasonable or probable cause and not necessarily an act done from ill feeling and spite. It is a deliberate act in disregard of the rights of others’. (A.P. V. Goverdhanlal Pitti, (2003) 4 SCC 739). Colourable exercise of power is equated with malice in law (Wadhwa V. Bihar, AIR 1979 SC 659) and in such a case, it is not necessary to establish that the respondent was actuated by a bad motive. (Venkataraman V. India, AIR 1979 SC 49). (Surendra Kumar Sinha, CJ). ...Government of Bangladesh =VS= Asaduzzaman Siddiqui, (Civil), 2019 (1) [6 LM (AD) 272] ....View Full Judgment

Mala fides signify with or in bad faith.
Mala fide is to be alleged with particularity- Assertion of general notice not sufficient for providing malafide. ….. [Lt. Col. Farzond Ali vs. Province of West Pakistan, (1970) 22 DLR (SC) 203]
Mala fide charge against Government not sustainable even though what it does is hard on a person and its order looks ugly. ….. [Tofazzal Hossain vs. Province of East Pakistan. (1976) 19 DLR 529]