NEW DELHI: AAP-Centre tensions seem to be escalating with the home ministry retracting its decision to appoint senior IPS officer Praveer Ranjan as chief of the Delhi government's anti-corruption bureau , overturning a specific request by the CM.Ranjan's appointment had been cleared on the request of Delhi chief minister Arvind Kejriwal and the move to revisit the decision comes in the wake of a vituperative confrontation between AAP and the Centre over the CM's demand for the suspension of four police officials.The Centre's relations with the AAP government, never too robust to begin with, have taken a beating after Kejriwal repeatedly targeted home minister Sushil Kumar Shinde , even leveling allegations of corruption against the senior Congress leader.Responding to Kejriwal's attacks, Shinde described Kejriwal as a "mad chief minister" at a function in Maharashtra.According to sources, the Centre's decision on Ranjan also comes in the wake of the appointment of about a dozen other Delhi Police officers to the ACB running into rough weather.However, the home ministry's latest move to refuse Kejriwal's request for a new ACB chief could have other ramifications as it challenges conventions governing relations between states and centre, and the right of state chief ministers to seek appointment of preferred officers.After the street dharna led by Kejriwal against Delhi police and the Centre, AAP government is believed to be preparing to direct the ACB to begin a probe against former chief minister and senior Congress leader Shiela Dikshit and her cabinet colleagues in cases relating to the 2010 Commonwealth Games. The Centre may well be keeping a close watch on these developments ahead of the Lok Sabha poll.According to available indications, almost a dozen other Delhi police officers that Kejriwal sought for ACB too may not be appointed. Delhi police and other sources suggest that the police may have told Delhi lieutenant governor Naseeb Jung that almost none of them want to come to ACB.The stance of the home ministry on the ACB chief's appointment is read as a clear sign that Congress doesn't intend to de-escalate its political tensions with AAP. Sources said on Thursday, the home ministry asked Jung to immediately relieve Ranjan from the Delhi police, where he is presently heading the economic offences wing, and to send him to Pondicherry.The home ministry's refusal to appoint Ranjan is the latest twist in AAP government's efforts to beef up its anti-corruption wing. On January 17, during the much publicised meeting between Kejriwal and home minister Sushil Kumar Shinde, when Delhi CM demanded control over the city police, the two had also discussed the appointment of Ranjan.When Kejriwal requested the posting of Ranjan, given his good reputation, as the chief of ACB, the home minister is believed to have said it was not a problem, and that whenever any chief minister asks for an officer of his preference the request is acceded to. Home secretary Anil Goswami, who was also present, assured that appropriate orders would be issued.But within a few hours the scenario changed. Kejriwal took to the streets against the home ministry's refusal to take action against police officials whom Delhi government held responsible for various lapses in the city. The CM slept by the Rail Bhavan on the street, and ended it after a deal was struck. According to reports, the Congress party was not pleased with the deal offered to Kejriwal to end his agitation.In the run up to his latest street agitation, Kejriwal also gave several interviews where he revealed Delhi government's immediate plans, that of investigating the alleged irregularities during Commonwealth Games and other major scandals of last Congress government.Sources said the Kejriwal government has already examining files from the PWD and other departments, of contracts in which several high profile officials and ministers including Dikshit were indicted by the CAG, Central Vigilance Commission and the Shunglu Commission. Kejriwal had publically announced that he would be ordering criminal investigations against Dikshit and her ministers in the alleged scandals.