Nick Clegg has come under fire over his plan to improve social mobility, with Labour claiming it is "mission impossible" with him at the helm.

In an angry Commons exchange, deputy leader Harriet Harman accused Mr Clegg of "betraying a generation of young people" by raising tuition fees.

But the deputy PM said Labour had failed to improve social mobility despite doubling public spending.

He said the coalition's "overriding mission" was to make society fairer.

Mr Clegg vowed to end the culture in which opportunity was determined by "who know you" - but admitted that he had benefited from an internship at a Finnish bank, secured as a result of "family connections".

'Tennis club'

The deputy prime minister faced questions in the Commons after unveiling the government's social mobility and child poverty strategies - entitled Opening Doors, Breaking Barriers.

As part of the plan, he announced that informal internships for young people in Whitehall would be banned.

"They should get an internship because of what they know," he told the BBC.

"It's not just because of someone who's met somebody at the tennis club or the golf club, who's whispered something into someone's ear and they've got an internship for their son or daughter."

In the end, it is a strategy - not a policy document or a set of spending commitments Read Mark's thoughts in full

The government says it is also asking all employers to commit to improving access to their internships and has already secured participation from organisations, including the Royal Academy of Engineering and the Association of Chartered, Certified Accountants.

But as part of an urgent question in the Commons, Ms Harman accused the government of launching "an assault on the opportunities for young people, especially the poorest".

"I'm afraid the deputy prime minister gave up the right to pontificate on social mobility when he abolished education maintenance allowances, trebled tuition fees and betrayed a generation of young people," she said.

"When I heard the deputy prime minister was going to launch a commission on social mobility I thought it was April Fools' Day.

"For many young people mobility has turned into a bus down to the job centre."

Ms Harman criticised a recent Conservative party fundraising event at which work placements at top financial institutions were auctioned off and accused Mr Clegg of "waltzing to the tune of the Tories".

And she added: "He may be a man on a mission but with him at the helm it's mission impossible."

Labour MP John Mann also attacked Mr Clegg, accusing him of "total hypocrisy" after it was revealed that his work experience between school and university was arranged through a friend of his father.

In response, the deputy PM told the London Evening Standard: "I do not deny that I have been lucky, but the plans I have set out today will help others from a much wider range of backgrounds to get the same opportunities I enjoyed."

Campaign group Intern Aware also claimed the Lib Dems were among the "worst offenders" when it came to offering unpaid internships and Mr Clegg must get the party's house in order.

'Born poor'

The government claims Labour spent billions moving people above the poverty line without significantly changing their children's opportunities.

It says that although just 7% of people attend independent schools, they make up 70% of High Court judges and 54% of CEOs of FTSE 100 companies.

Universities Minister David Willetts told BBC Radio 4's Today programme: "We are pulling together all of the different crucial stages as people go through their lives when key decisions or events shape their futures.

"And we are trying to show, for each one of them, how we are going to improve social mobility and improve opportunity."

The government has appointed former Labour minister Alan Milburn to monitor its progress on a series of indicators, including whether top universities are allowing enough state-school educated children in.

He told the BBC: "Sadly, we still live in a country where, invariably, if you're born poor, you die poor. Just as if you go to a low-achieving school, you tend to end up in a low-achieving job."

But the University and College Union, which represents lecturers and other staff, said raising tuition fees and scrapping the Education Maintenance Allowance would counteract any attempt to improve social mobility.

Its general secretary Sally Hunt said: "Education is the closest thing we have to a silver bullet when it comes to social mobility, yet since this government took power, we have seen major financial barriers erected in the face of those from low and average-income backgrounds. "

Think tank million+, which represents many newer universities, said government had overlooked the efforts made by those institutions to get students from poorer backgrounds into good careers.

"Instead, the obsession with getting a small number of younger students from poorer backgrounds to Oxbridge shows a worrying lack of appreciation of the achievements and the quality of the teaching provided in modern universities," chief executive Pam Tatlow said.

"If ministers want to do more, they should challenge the old-fashioned and elitist views in government about the quality and value of universities and do much more to challenge employers who only recruit from a small number of universities."

The campaign to save the Education Maintenance Allowance - paid to 16 to 19-year-olds in the UK to help them stay in education - accused Mr Clegg of hypocrisy.

Campaign chief James Mills said: ""Cameron and Clegg probably never had to worry about bus and train fares or how to travel to college at their boarding schools but it's not like that for ordinary teenagers in the UK.

"It's not their fault they can't relate, but it is their fault they refuse to understand."

The government has announced a £180m bursary scheme to replace EMA, which was scrapped in England last year.

EMA schemes in Scotland and Wales are continuing - and the allowances in Northern Ireland are under review.