UK pharmaceutical group GlaxoSmithKline (GSK) is facing rebellion from its shareholders as they call for an early departure from chairman Christopher Gent, reports said.Gent has been GSK's chairman for nine years, and announced earlier this year he would resign in 2015. However, shareholders worried with the company's underperforming share price and alleged bribes in China want him to resign this year, The Sunday Times reported.Phillip Hampton is believed to replace Gent next year after he steps down as chairman of Royal Bank of Scotland.The pharmaceutical company is being accused of earning billions of renminbi by bribing Chinese hospital officials to use its medical products. In July, Chinese authorities arrested a number of GSK executives over the bribery scandal. A British investigator and his wife were also among the arrests. Peter Humphrey and Yu Yingzeng were arrested last month accused of obtaining personal information and selling it to multinationals including GSK.GSK's chairman said last year: "The allegations of fraudulent behaviour by certain employees within our business in China are wholly contrary to the company's values and we take this matter extremely seriously."The company's shares have dropped 10% in the past year and were down a further 1.2% at 1,457.43p by 14:51.JF