Ed Miliband has branded David Cameron a "tainted prime minister" whose failure to stand up to the rich and powerful makes him unable to deliver the change which Britain needs.
Describing the Conservatives as "part of the problem", Mr Miliband said the UK's return to recession has shown Mr Cameron and his party to be tied to a set of outdated and ineffective economic, social and political orthodoxies which are "crumbling before our eyes".
As the prime minister prepares to attend the G20 summit in Mexico, Mr Miliband said the world needs new economic leadership to deliver a global plan for jobs and growth.
He seized on evidence from the Leveson Inquiry of Mr Cameron's close links with senior figures at News International, arguing that it shows him to be someone who stands up for "the wrong people".
In a speech to Labour's National Policy Forum in Birmingham, Mr Miliband said his party's task is to "rebuild Britain" so it works for everyone, and not just a powerful and privileged few.
Describing the next steps in Labour's policy review, Mr Miliband said it will focus on three themes: rebuilding the economy, rebuilding society and rebuilding politics.
He set out his "vision for our future economy", where companies would be regarded as a shared project between workers, management, shareholders and customers, with reduced pay inequality and an end to poverty wages.
Mr Miliband said he wants to create a more equal society, built on "care, compassion and real reciprocity, not just on money, market and exchange".
Labour must restore confidence in politics by "standing up for the many against the interests of the few, however powerful they are", he told his party. He added: "The scale of the crisis we face is enormous."
Conservative Party Deputy Chairman Michael Fallon said: "Ed Miliband was a central figure in Gordon Brown's old team that was known for briefing against a sitting Prime Minister, abusive behaviour and negative spin. Labour were just as close to the Murdochs and to try to score cheap points on this issue is rank hypocrisy."