The Eurosceptic MP says her party's ambiguity towards Britain has alienated working class voters.
The party is divided over whether the presence of the left-winger on the ballot will help or hinder it.
The party will need to decide whether to make the case for investment or to embrace fiscal conservatism.
Frontrunner Burnham warns that Labour must "take care not to distance ourselves from the last five years" on the issue of inequality.
The former leader has quickly taken up the cause he championed in office.
The arithmetical Everest facing the party means Miliband's successor may find it even harder to convince anyone they can become prime minister.
Ahead of Brussels visit, leadership candidate says he will "learn the lessons of the Scottish independence referendum" by not joining forces with the Conservatives.
MPs consider alternatives after "break clause" is rejected by acting leader Harman.
Labour leadership candidate becomes the first to formally pass the nominations threshold of 35.
By adopting a pro-business message and admitting the deficit was too high, the Labour leadership candidate has frustrated hopes he would turn left.