Ed Miliband has announce his resignation after a crushing defeat for Labour at the polls during which several high-profile politicians lost their seats.
Miliband said it was “time for someone else” to take over the leadership and that he was “truly sorry” he did not succeed.
Deputy leader Harriet Harman will act as deputy leader of the party until a new leader is elected, after which she too has said she will step down.
The SNP made huge gains in Scotland, winning 56 of the 59 constituencies, including Scottish Labour leader Jim Murphy and election campaign chief Douglas Alexander. In comparison, in 2010 the SNP won just six seats.
Shadow Chancellor Ed Balls was another Labour heavy-weight to lose his seat, by just 422 votes. His former constituency Morley and Outwood went to Conservative Andrea Jenkyns.
Speculation now reigns over over who might replace Miliband as party leader. The party have said that shadow home secretary, Yvette Cooper, the shadow health secretary, Andy Burnham, the shadow justice minister, Dan Jarvis, the shadow health minister, Liz Kendall, and the shadow business secretary, Chuka Umunna, could be potential candidates for the post.