Gordon Brown has staked his claim for Labour to be the party of an expanding middle class, so rejecting any suggestion he would make a narrow electoral appeal to the party's "core vote".
Writing in the Guardian, he says he wants to create an aspirational middle class, and a society of social mobility in which the glass ceiling is not merely raised but broken: "Opportunity and reward cannot be hoarded at the top and it is not enough to protect people at the bottom."
Promising to unleash the "biggest wave of social mobility since the second world war" he says his aim is to create "a genuine meritocracy".
He rejects any suggestion social mobility and social justice are at odds, saying his aim is to create "an expanded middle class, not a squeezed middle class".
In his speech tomorrow he will say: "I believe that character is formed not on the mountaintops of life when things look easy, but in the valleys when things are tough."
The prime minister's electoral positioning comes ahead of the government's response on Monday to a report on access to the professions, chaired by Alan Milburn, a former Labour cabinet minister. It is expected ministers will accept the vast bulk of the Milburn commission's 80 recommendations.
In his report, Milburn argues that a "closed shop Britain" must end. On Monday, the government is expected to propose 1,000 higher education places or scholarships be reserved for apprentices, a life-long skills account to help children progress from further education and fresh advice to universities to take into account the context in which a school child secured their exam mark. The government is also expected to propose a revamp of the much criticised school careers advice service.
In his Guardian article, Brown argues that the potential to create a new wave of professional jobs – estimated to grow by seven million by 2020 – can only be brought about through an active industrial policy.
"The difference between Labour and Conservative is that the Conservatives reject industrial strategy as a matter of ideology."
Brown also appears to recognise the election cannot be fought on the old dividing line that saw Labour win the past three elections.
"After the global financial crisis, it will be the first election of a new age, unlike any election I have fought before," he writes."