The hung parliament could delay Brexit negotiations, as the surprise result hammered the British pound.
The prime minister and the leader of the opposition refused to join TV debates, making the election result seem more of a foregone conclusion than ever.
The unpredicted result in the tight election came after Conservatives trounced Labour in key seats.
Final opinion polls showed Prime Minister David Cameron's Conservatives and Ed Miliband's opposition Labour Party almost in a dead heat.
The two main parties have been neck-and-neck in most opinion polls since the start of the year, with neither establishing a sustained lead.