Sir Keir Starmer has announced he will step down as the MP, triggering a by-election in his London seat and prompting the first major political test for his successor Andy Burnham.
Sir Keir resigned as prime minister in July to make way for Mr Burnham after he lost the support of his party in the wake of dire local election results, the scandal over appointing Peter Mandelson as ambassador to the US and a failure to deliver on key policies including welfare reform.
