Ed Miliband is to brand 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Mr Miliband will say that the UK's return to recession has revealed Mr Cameron and his party to be tied to a set of outdated and ineffective economic, social and political orthodoxies which are "crumbling before our eyes".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 will say that the world needs new economic leadership to deliver a global plan for jobs and growth.
He will seize 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 will say that 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 will say it will focus on three themes: rebuilding the economy, rebuilding society and rebuilding politics.
He will 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 will also say he wants to build 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", Mr Miliband will tell his party.
"The scale of the crisis we face is enormous," he will say. "The task we face is no ordinary task for an Opposition. It is certainly not the time to carry on as we did before. It is not the time to try to make do and mend. Our task will be to rebuild Britain. To rebuild our economy. To rebuild our society. To rebuild our politics. So that we can rebuild our country to ensure that it works for everyone, and not just a powerful, privileged few."