Ed Miliband has promised to "rebuild our middle class" in the face of a cost-of-living crisis.
The Labour leader said a "strong and vibrant" middle class was essential for the country's success but its foundations were being undermined and threated by the current Government.
There has been a "hollowing out" of white collar professions and the prospect of rising living standards for future generations is being put at risk, he said.
Writing in The Daily Telegraph Mr Miliband said the squeeze on living standards was not just affecting the poorest in society but meant a "struggle" for those in the middle.
Ahead of a major speech on the economy later this week, the Labour leader said: "Our country cannot succeed and become collectively better off unless Britain has a strong and vibrant middle class."
Acknowledging the long history to the problem, he said: "According to government figures, the occupations that have suffered the largest falls in employment over the past 30 years are all in the middle."
But, he added: "Under David Cameron, life is getting tougher still. In the past three years, getting on for half of the new jobs created have been in low-pay industries and the average worker is now £1,600 worse off than before the election."
Setting out the fundamental threat to the expansion of the middle class, he said: "The British middle class is being squeezed by a cost-of-living crisis as never before - and people grafting to join it find that the obstacles in their way are getting bigger.
"The motors that once drove and sustained it are no longer firing as they used to. Access to further education and training, good quality jobs with reliable incomes, affordable housing, stable savings, secure pensions: they have all been undermined."
He said that "no one saw this protracted squeeze on the middle coming".
"My own party's politics changed in the 90s to surf a wave of aspirational self-confidence," Mr Miliband said.
"But the task facing the next Labour government will be far different from the one we faced in 1997. Indeed, the greatest challenge for our generation is how to tackle a crisis in living standards that has now become a crisis of confidence for middle-class families."
The newspaper reported that Mr Miliband's plan to tackle the problem includes a toughening of the party's position on welfare to link benefits payment to employment history, so those with a record of work qualify for higher handouts than those who have never had a job.
As the economy has recovered, Labour has shifted the focus of its attack on the Government to the rising cost of living, with prices rising faster than wages.
Mr Miliband's latest intervention is intended to highlight how the problem hits all sections of society, including those in the middle class who thought they would be comfortably off.
He said: "The cost-of-living crisis is not just about people on tax credits, zero hours contracts and the minimum wage. It is about millions of middle-class families who never dreamt that life would be such a struggle."
Conservative Party chairman Grant Shapps said Labour were to blame for the recession, before slamming the opposition leader for having "no plan."
"Many people who work hard are facing tough times today because they have been made poorer by the worst recession in a century - a recession presided over by Ed Miliband and the Labour government he was part of.
"The only way to ensure a better and more financially secure future for hardworking people and for their children is to stick to David Cameron's long-term economic plan - reducing the deficit, creating jobs, cutting taxes, giving young people the skills they need to get on and fixing the welfare system so that it pays to work.
"But Ed Miliband has no plan. He has opposed every difficult decision we have taken to start turning our economy around. All he offers is more of the same old Labour policy that got us into a mess in the first place - more spending, more borrowing and more taxes. That would mean a less secure future for hardworking people and their families."