The Congress on Tuesday took potshots at the Delhi government over the resignation of Transport Minsiter Gopal Rai, saying in just a year half of Chief Minister Arvind Kejriwal's cabinet has been removed on various charges."Half of Kejriwal cabinet removed on corruption, cheating and inefficiency in one year! Transport Mininster Gopal Rai resigns -- premium bus investigation starts," Delhi Congress President Ajay Maken posted on Twitter."Premium bus investigation" refers to the probe by the anti-corruption branch (ACB) into allegations of favouritism underlying the notification of a policy to enable app-based premium buses in the capital as a ploy to extend benefits to a Gurgaon-based private operator.Earlier Maken tweeted: "In wake of premium bus service investigation - Transport Minister Gopal Rai resigns... Or is he being shunted out for dismal public transport?"The ruling Aam Aadmi Party (AAP) on Tuesday said Rai was leaving "on health grounds". The ACB probe started on the basis of a complaint filed by Bharatiya Janata Party (BJP) legislator Vijender Gupta, who has alleged that the AAP government was "trying to benefit" a particular private bus aggregator.