"In India, the net worth of the billionaire community increased twelve-fold in 15 years, enough to eliminate absolute poverty in this country twice over," said Lagarde delivering the Richard Dimbleby Lecture in London, according to the copy of the speech made available by the IMF.
"We are all keenly aware that income inequality has been rising in most countries. Seven out of ten people in the world today live in countries where inequality has increased over the past three decades," she said adding that the richest 85 people in the world own the same amount of wealth as the bottom half of the world's population.
In the US, inequality is back to where it was before the Great Depression, and the richest 1 percent captured 95 percent of all income gains since 2009, while the bottom 90 percent got poorer, Lagarde said ruing that in the past, economists have underestimated the importance of inequality.
"They have focused on economic growth, on the size of the pie rather than its distribution.
"Today, we are more keenly aware of the damage done by inequality.
"Put simply, a severely skewed income distribution harms the pace and sustainability of growth over the longer term.
"It leads to an economy of exclusion, and a wasteland of discarded potential," Christine Lagarde said.
Observing that over the next three decades, the worlds population will get much larger and much older, she said in 30 years time, there will be about two billion more people on the planet, including three quarters of a billion people over the age of 65.
By 2020, for the first time ever, there will be more old people over 65 than children under five, she added.
"The geographical distribution will also change - young populations in regions like Africa and South Asia will increase sharply while Europe, China, and Japan will age and shrink.
"In the coming decades, we expect India to surpass China, and Nigeria to surpass the United States, in terms of population.
"And both China and India will start ageing in the near future," Christine Lagarde said.
"This can create problems on both ends of the demographic spectrum for youthful countries and for greying countries.
"Right now, the young countries are seeing a 'youth bulge', with almost three billion people, half the global population, under age of 25.
"This could prove a boon or a bane, a demographic dividend or a demographic time bomb," she said.
"A youthful population is certainly fertile ground for innovation, dynamism, and creativity.
"Yet everything will depend on generating enough jobs to satisfy the aspirations of the rising generation," Christine Lagarde said adding this called for a single-minded focus on improving education...
"Looking ahead, factors such as the internet revolution, the rise of smart machines, and the increasing high-tech component of products will have dramatic implications for jobs and the way we work.
"Yet governments are not thinking about this in a sufficiently strategic or proactive way,"Christine Lagarde added.