Labour is promising to help up to 130,000 of the "brightest" young people from poorer families with getting to college and university.
Prime Minister Gordon Brown said they would get a "structured package of support" from 2012, to help break the "glass ceiling of social mobility".
He also pledged to set up a Social Mobility Commission, to report later.
Labour says it wants to encourage top professions and universities to attract more people from deprived backgrounds.
Its proposals follow a report by former cabinet minister Alan Milburn's report saying areas like medicine and law were dominated by people from affluent families.
Labour's plans for social mobility - which would depend on it winning the general election - were part of Gordon Brown's attempts to "portray Labour as the party of aspiration".
'Denied the chance'
Meanwhile, as the two main parties battle to win the middle-class vote ahead of the election expected in May, the Conservatives are calling for teaching to become a "brazenly elitist" profession, restricted to the best graduates.
In his response to Mr Milburn's report, Mr Brown said: "My mission is to ensure that all of Britain's people, from every background, are given the opportunity to develop their talents and learn the skills which will transform their lives. And this social mobility must be rooted in our core value of fairness.
Nick Robinson
"In many ways society is already fairer. Six hundred thousand children have been lifted out of poverty, record numbers of our young people are going to university, one in three people of working age is a member of a profession, and the gender pay gap has narrowed.
"But we can't be a truly aspirational society if some people are still denied the chance to get on, and although we have raised the glass ceiling we have yet to break it.
"That is why our priority will be to remove all the barriers that are holding people back."
In his report, Mr Milburn said careers such as law and medicine were dominated by people from affluent backgrounds.
The "vast majority" of his 88 recommendations are being accepted by the government and the former minister will help to establish a commission to track progress.
A new forum will tell the top professions to come up with plans to widen their pool of recruits.
And a national internship service will give experience of these careers to more students and graduates.
The Conservatives have questioned why Labour has not done more to improve social mobility after 12 years in power.
