​Washington, May 19 (IANS) The US Labour Department has agreed to increase overtime rates for workers amid a continuing shrinking of the middle class.

The rule will increase protection of over 4.2 million workers by doubling the payment threshold for working over 40 hours a week from $455 per week to $913 dollars, Xinhua

news agency reported.

The threshold will be automatically improved every three years from January 1, 2020, according to the rule which will come into effect on December 1 this year.

The move is expected to boost wages for workers by $12 billion over the next 10 years, said the White House, adding that overtime protections in the US had eroded as a result of inflation and lobbyists' efforts to weaken them over the past 40 years.

The US middle class has been losing ground. The share of middle class to the whole US population fell from 55 percent in 2000 to 51 percent in 2014, said a survey by Pew Research Centre.​