O'Grady was commenting on a report by think-tank the Resolution Foundation, which has found the number of low-paid workers (those earning less than two-thirds of the median hourly rate) rose by 250,000 in the past year.
The research also suggests that one-quarter of those currently earning minimum wage have been doing so for five years or more. The minimum wage is set at £6.50 per hour, having increased by 19p at the start of October.
On 18 October around 90,000 people demonstrated across the UK to encourage business to increase wages for lowest-paid workers. O'Grady said this report "shows why" people have taken to the streets.
"Many of the jobs created since the crash are of the low-paid, casual and zero-hours variety," she said. "This risks many people and their families being left behind, unable to share in any benefit from the economic recovery, while those at the top take an increasing share of the nation’s wealth."
“What’s more, once in a low-paid job it can be hard, if not nigh on impossible, to get higher paid work," she added. "Without a new approach it’s quite likely that the overwhelming majority of the five million workers currently in low-paid work will still be stuck there a decade from now.”