Amid an ongoing tussle between the Centre and West Bengal government, state chief secretary Alapan Bandyopadhyay yesterday retired from his post and joined chief minister Mamata Banerjee as her chief adviser. Bandyopadhyay was originally set to retire yesterday but was granted a three-month extension. In a media briefing, Mamata said she has appointed Bandyopadhyay as her chief adviser for the next three years. However, the central government sources warned of stern action against Bandyopadhyay. The rejig comes in the backdrop of a major row between the Centre and state government that was triggered by Mamata's hurried appearance during a cyclone review meeting with Prime Minister Narendra Modi.