The stark gap between Britain's best and worst-performing cities has "dramatically widened" over the past decade, a new study has shown.
And nearly four out of 10 households with children, or 8.1 million people, are too poor to participate fully in society, according to a separate study.
For every 12 jobs created since 2004 in cities in southern England, only one was created in cities in the rest of the country, research found.
The research comes as David Cameron is set to make employment the centre of his re-election campaign, promising to keep Britain the "jobs factory of Europe" by backing small business.
"Full employment may be an economic term, but this is what it means in human terms: it means more of our fellow men and women with the security of a regular wage; it means you, your family and your children having a job and getting on in life," Cameron said.
"We have had a tough few years as a country, but we are coming out the other side. We are the jobs factory of Europe; we're creating more jobs here than the rest of Europe put together. That's what our long-term plan means for you - and if you vote Conservative, we can stay on this road to recovery."
But the Centre for Cities research group said national economic growth had been largely driven by only a handful of cities, mainly in the South. Jobs in London increased by more than 17% between 2004 and 2013 while Blackpool, Rochdale and Gloucester saw falls of 10%, said the report.
There was also a huge difference in populations, growing by 16.5% in Milton Keynes and falling by 1.4% in Sunderland. The number of new businesses varied - up by almost a third in Swindon but down by 5.5% in Grimsby.
Andrew Carter, acting chief executive of Centre for Cities, said: "Five months out from the election, this report makes the strongest economic case yet for the next Government to step up to the challenge of investing in the long-term success of our cities, and build a brighter future in which more people and places can contribute to, and share in, prosperity and growth.
"The stark picture the report paints of the enormous gap in the fortunes of UK cities over 10 years underlines why a 'steady as she goes' approach must be scrapped.
"We must move from thinking that bundling up new funding streams with bureaucratic delays, or simply tinkering around the edges with well-intentioned announcements, will be enough to reverse trends that are becoming increasingly entrenched."
Ed Cox, director of IPPR North, said more powers needed to be devolved to regions to help them create prosperity and ensure smaller places do not fall behind as core cities grow.
Cities Minister Greg Clark, said: "This Government's long-term economic plan is working right across the country. Since 2010 over 60% of the rise in employment has taken place outside London and the South East - that's over a million more people in work.
"We know there is more to do and that's why we have given greater powers to 27 of the UK's largest cities through City Deals, and why we have committed a further £7 billion to the north of England, alongside the ground-breaking devolution deals and £6 billion of Growth Deals in every part of England."
Shadow business secretary Chuka Umunna said: "Centre for Cities' 2015 Cities Outlook highlights the huge potential for more balanced growth across Britain by devolving powers and budgets. The Tory-led Government came to office promising to rebalance the economy but instead we've seen too many parts of Britain held back and the benefits of growth being concentrated in the hands of the few. Under this Government, cities with the greatest needs have been hit hardest.
"The next Labour government will push power away from Whitehall and give city and county regions and local areas the powers they need to boost local growth. Under our plans £30bn of budgets would be devolved down and combined authorities would be able to keep more of their revenue from business rates so they can benefit from additional growth."
The figures come as the Joseph Rowntree Foundation revealed more than eight million people have an income level than £16,284, regarded by the greater public as the minimum needed to participate in society.
That definition, which was ascertained through discussion with focus groups, includes the ability to pay for a week’s holiday in the UK and to run a second-hand car, but does not include eating or drinking out or smoking cigarettes.
Katie Schmuecker, policy manager at the Joseph Rowntree Foundation, said: “There has been a turnaround in who is suffering most as a result of the economic crisis and government measures to reduce the deficit.
"While last year’s monitoring report showed a sharp rise in young single people struggling to make ends meet, this year’s report shows a rapid widening of the gap between the incomes and costs of families with children.”