More than 3.5 million children and young people were living in households receiving Universal Credit (UC) before the uplift was removed, the latest figures show.
There were more than 1.9 million households, containing more than 3.5 million children and teenagers, receiving the benefit as of August 2021, according to the Department for Work and Pensions (DWP).
This is out of a total of 4.9 million households.
A temporary £20 a week uplift, introduced to help claimants weather the storm of the coronavirus pandemic and described as a “lifeline”, was phased out over the past month.
The latest quarterly figures, published on Tuesday, are the first to be published since the extra money was removed.
Figures showing how many households were receiving UC in October, when families received their first payments without the uplift, will not be published until February.
The data is also the first to be published since the furlough scheme ended on September 30, although the DWP said it is too early to assess any impact on UC claims.
There were 5.8 million people on UC on October 14, according to provisional data in the release, down 67,000 from July 8.
Women accounted for 54% of recipients, and, as of September 9, 40% of UC recipients were employed.
Households without children accounted for around 55% of the households on UC, down three percentage points lower than in August 2020.
There were an average of 33,000 new starts to UC per week in the five weeks to October 14, up 9% from the four weeks to September 9.
Dan Paskins, director of UK Impact at Save The Children, said many parents are “constantly worried” about paying for food and bills, with children paying the price through missing out on experiences such as school trips.
He said: “We welcomed the Government’s adjustments to Universal Credit in the Budget.
“But allowing some people to keep more of their income is not a replacement for a strong social safety net that protects everyone in our society.
“Ministers must do more to protect children across the UK from cold and hunger this winter.”
A Government spokesman said: “This Government is committed to supporting families and people in need, we have provided billions of additional welfare support through the pandemic and continue to do so.
“Work is the best route out of poverty and the changes we have made to Universal Credit will see nearly two million working claimants better off by around £1,000 a year.
“The most vulnerable, including those who can’t work, can get additional benefits, and help with essential costs is available through our new £500 million support fund.”