FILE: Conservative Party starts 100-day countdown to UK election Britain is revving up for one of the tightest and most unpredictable elections in memory, as Prime Minister David Cameron fights to retain power and call a referendum on European Union membership. As the 100-day countdown to elections begins Tuesday, experts predict that neither the Conservatives nor Labour will secure a majority in the 650-seat House of Commons. FILE IMAGES of the last Conservative Party conference for illustration.