Describing Reserve Bank of India (RBI) Governor Urjit Patel's resignation as "unprecedented", West Bengal Chief Minister Mamata Banerjee on Monday said the credibility of all institutions is being "destroyed".She expressed her concern over Patel's quitting and said this was a "financial and economic emergency"."This has never happened before. This is unprecedented. We are deeply concerned. The RBI is the custodian of public money. The credibility of all institutions is being destroyed. This is a financial and economic emergency," Banerjee tweeted.Patel resigned from his post on Monday with immediate effect, citing "personal reasons".