HSBC, Europe's biggest bank, has ordered a review into whether it should move its headquarters out of Britain and potentially back to its former home in Hong Kong, threatening London's reputation as a global hub for finance and investment. The announcement from HSBC, founded in Asia but a key part of the British establishment, prompted a warm response from Hong Kong, where it is revered as "The Bank", and silence from the British government. The commitment to the review comes less than two weeks before British parliamentary elections on May 7 and poses challenges for both Prime Minister David Cameron and his main challenger, Labour party leader Ed Miliband. HSBC has been one of the most vocal critics of the regulations and additional taxes imposed on British banks in the wake of the 2007-2009 financial crisis and Chairman Douglas Flint singled out the threat of Britain withdrawing from the European Union in a speech to investors on Friday.