More than a million Londoners living in poverty are in a working family, a massive increase of 70% over the past decade, according to new research.
More than a quarter of people in the capital are now said to be in poverty compared with 20% across England, the study found.
The report by New Policy Institute, funded by the Trust for London charity, said improving employment prospects had not been enough to lift people out of poverty in London.
The number of low-paid jobs is up for the fifth year in a row, with almost one in five not paying the London Living Wage, while 1.2 million people in poverty live in a working family, said the study.
Other "striking" findings include temporary work contracts at a 10-year high and a 19% increase in rents in the past five years, compared to a figure of 11% for England.
The average private rent in London is now £1,600 a month, more than double the average for England.
The report's author Hannah Aldridge said: "When people talk about 'generation rent', they normally think of young working adults unable to save a deposit. But the 260,000 children growing up in private rented poverty are at the sharp end of London's housing crisis, living in expensive, often low-quality homes without long-term security.
"Affordable starter homes at £450,000 won't solve this problem - London needs investment in more housing suitable for a range of families and incomes, and it needs greater powers to ensure private accommodation is of a good standard."
Mubin Haq, director of policy and grants at Trust for London, said: "A record number of Londoners are in work, yet this has had little impact on the numbers living in poverty in the capital. Over two million are on a low income in London, with an increasing number in working families. On too many occasions work doesn't pay enough, leaving people living in precarious situations.
"Action is also needed on costs, particularly in relation to housing. The numbers of affordable homes being built is a fraction of what is needed."
Child Poverty Action Group chief executive Alison Garnham said: "Today's findings show just how hard it is already for low-paid London parents to meet their bills and how incredibly dangerous it would be to cut their tax credits.
"Up against sky-high housing and childcare costs, these are the hard-working families whose budgets will be badly damaged by the cuts proposed. Around 38% of children in the capital already live in poverty - more than in England and Wales combined. Unless the Government listens to the many cross-party critics of tax credit cuts, that number can only rise."
Campbell Robb, Shelter's chief executive, said: "It's heart-breaking to know that in one of the wealthiest cities in the world, hundreds of thousands of children are living in poverty because of our housing shortage.
"Sky-high housing costs and spiralling rents are leaving families across the capital struggling to make ends meet, not knowing whether they'll have a roof over their heads from one month to the next.
"Yet year after year, we keep failing to build the genuinely affordable homes we need to tackle this crisis once and for all. With the mayoral elections coming up next year, the candidates have a real chance to grab the bull by the horns and show voters they are serious about fixing this shortage and giving children back the hope of a brighter future."
The study looked at income and housing costs in the capital to define poverty.
TUC general secretary Frances O'Grady said: "Work simply isn't paying enough for many Londoners. They work hard, but still find their families living in poverty. The Government has failed to deliver the decent wages and affordable homes working Londoners need.
"If the Government goes ahead with its cuts to in-work tax credits, even more working families will be pushed into poverty across the UK."
A Government spokesperson said: "Living standards are rising – over the last year real earnings rose by 2.8%, the fastest rate of growth since September 2007 and the number of children growing up in workless families is at a record low.
"But there's more to be done. That's why we are introducing a new national living wage which the independent OBR expect will benefit up to 2.7 million people directly – 200,000 of which are in London. Together with the further increases to the personal allowance next year, this will mean people will keep more of the money they earn by paying less income tax.
"Our affordable house-building efforts have exceeded ambitions and delivered more than 260,000 affordable homes, 35,000 of which have been built in London"