The UK is still a "long distance" from becoming a classless society, Nick Clegg warned today.
Outdated, snobbish attitudes are "cramping" society and "hobbling" the economy and must be shaken off, the Deputy Prime Minister said.
The Lib Dem leader added it was a "damning indictment" on the UK that some people are born with a sense of entitlement, while others simply face exclusion.
In a speech to the Sutton Trust in central London earlier today, Mr Clegg said: "Too often, the question of class and class attitudes is left in the shadows of the social mobility debate.
"Politicians are often reluctant to get into a discussion about class especially if, like me, they have been fortunate in their background, schooling and opportunities.
"But we can't ignore it. Class still counts. We are a long distance from being a classless society.
"And I don't only mean in the hard material facts - inequalities in income, health and wealth. I also mean in terms of the attitudes and assumptions we carry around in our heads - about ourselves and about others.
"Eighty years ago, the historian Frank Harris declared that: 'Snobbery is the religion of England'. I think that statement still has more than a ring of truth today."
Mr Clegg said that at one end of the spectrum there are those who feel almost a sense of entitlement to the best schools, universities and jobs.
"Advantages are handed down almost automatically, generation to generation," he said.
"Surrounded by peers, parents, teachers and other role models promoting a sense of aspiration and possibility, the most fortunate see the horizons of their opportunities stretched far in all directions.
"And so from day one, they hear a clear, self-confident message. One that says: 'The world is yours. Go for it'."
Mr Clegg insisted that this message should be heard by everyone, but that many children from poorer homes look at certain qualifications, schools, universities and jobs and believe they are not meant for them, because that is what they are continually told.
One in two parents from higher social classes expect their child to get a job in a profession, compared to one in five of those from the lowest social backgrounds, he said.
And one in five teachers say they never advise their brightest students to apply to Oxford and Cambridge.
"To me, that is a damning indictment on all of us," Mr Clegg said.
"We end up with entitlement at one end and exclusion at the other.
"A closed society, in which people know their place.
"We need an open society, in which people choose their place.
"As a nation we have to shake off the outdated, snobbish attitudes of class that are cramping our society and hobbling our economy."
The coalition is committed to examining national progress on encouraging social mobility, and to push ahead with plans to boost the life chances of poorer youngsters, Mr Clegg said.
Mr Clegg was speaking as the Government published a raft of new trackers designed to measure progress in making society fairer.
The 17 indicators cover areas including readiness for school, the attainment of youngsters on free school meals at age 16 compared with their peers, and the proportion of poorer children going to university.
It will be the first time that any government in the world has published such information, according to the Cabinet Office.
The trackers, which will be published annually, are included in the Government's first update of its social mobility strategy Opening Doors, Breaking Barriers: A Strategy For Social Mobility.
The document shows that, at age four, 44% of children eligible for free school meals - a key measure of poverty - are reaching the standard of achievement expected for their age group, compared with 62% of their richer classmates.
At age 16, just a third (35%) of poorer pupils are reaching the level expected, compared with almost two-thirds (62%) of other pupils.
And less than a fifth (17%) of poor teenagers go on to university, compared with 35% of their peers.
Mr Clegg said: "We must create a more dynamic society - one where what matters most is the person you become, not the person you were born.
"Government cannot do this alone, but we must take the lead. So we're exposing the stark gaps in life chances by publishing a wide range of tracking data to show how well society is doing here and now.
"No government has done this. The data shows we've got a long way to go, but that's why it's there - to hold a flame to our feet until the gaps close. It's not an overnight fix, but it is a long- term ambition that is achievable."
Mr Clegg also insisted that making efforts to secure better life chances for children from poorer backgrounds does not mean lowering standards.
False claims of "dumbing down" are myths used by elites seeking to entrench their unwarranted privilege, he told today's conference.
"The myth is that the promotion of social mobility means lowering standards, or somehow dumbing down, to socially engineer a particular outcome," he said.
"This is nonsense. Nonsense, I should add, which is usually peddled by those who benefit from the status quo - and therefore want to keep things the way they are.
"Social engineering is what's happening now: the unfairness in our society, and the system that perpetuates it,
Mr Clegg himself benefited from a public school and Oxbridge education, but he dismissed critics who suggest that undermines his ability to tackle the subject.
"I know some people will say I should keep quiet about social mobility, that my birth, my education and my opportunities mean I have no right to speak up," he said.
"I couldn't disagree more. If people like me who have benefited from the system don't speak up, we will never get anywhere."
Defending attempts to widen the pool of pupils going to top universities, he said recruitment should be "on the basis of an ability to excel, not purely on previous attainment".
Labour deputy leader Harriet Harman said: "Nick Clegg would have more credibility on social mobility if he hadn't promised to scrap tuition fees before the election, and then trebled them afterwards.
"He's part of a Tory-led Government which is closing children's centres and has scrapped the Education Maintenance Allowance and the Future Jobs Fund, while more than a million young people are out of work - and which is failing to take forward key measures in Labour's Equality Act to narrow the gap between rich and poor.
"Cutting taxes for millionaires while millions pay more makes inequality worse, not better."
Sir Martin Harris, director of the Office for Fair Access, which ensures fair access to university, said: "I warmly welcome the recognition in this report that raising attainment and aspiration in schools is a vital factor in fair access to higher education for all bright and able children, regardless of their background. Indeed, the Office for Fair Access has pointed to this for some time.
"I also agree that greater clarity, earlier on, about financial support for students could be very helpful, so they have all the facts when making key choices.
"As both the Government and Ed Miliband have reiterated in recent days, fair access to university is of course essential to social mobility. That is why, since 2006, universities that wish to charge higher fees have agreed 'fair access' agreements with the Office for Fair Access setting out how they will work to attract disadvantaged students, including outreach activities and financial support such as bursaries."
Sally Hunt, general secretary of the University and College Union (UCU), said: "Nick Clegg has consistently made positive noises about the importance of social mobility and it would be unfair to suggest it is not something he feels strongly about.
"However, his warm words will never be a substitute for government policies that would genuinely help the poorest people in society access education."
She added: "Education is the closest thing we have to a silver bullet when it comes to social mobility. However, we have seen university fees rocket, vital college grants axed and now plans to force young adults to take out huge loans if they wish to return to education.
"It is difficult not to conclude that the greatest threat to social mobility at present is this Government's punitive policies."
James Westhead, director of external relations at Teach First said: "Teach First welcomes the focus this week on social mobility from both the Deputy Prime Minister and the Leader of the Opposition. Both recognised the crucial role education plays in driving greater social mobility.
"In too many communities in Britain, how well you do at school can be predicted by the income of your parents.
"It doesn't have to be this way. We know from working in schools across seven regions in England that the quality of teaching and leadership in a school can enable children to overcome social disadvantage."