More than 24,000 people in Newham will lose £1,000 per year when the uplift to universal credit ends this month.
The £20 reduction will see 24,190 recipients of the benefit each lose £1,040 a year, which will lose Newham a total of £25,157,600, according to the mayor's office.
Mayor of Newham, Rokhsana Fiaz, said: "We’re still in this crisis. Families in Newham are desperately struggling to get back on their feet, yet this government wants to kick their legs out from under them.
"Whacking families with a £1,000 cut in support won’t just hurt them, it will hammer the local economy too.
"These proposals will take food off the table and more than £25million out of the local economy.
"Yet at the same time as the Conservatives hammer working people, we know they can find £2billion for crony contracts for their friends and donors.
"That tells you everything you need to know about whose side this government is really on – and it’s not us here in Newham."
A government spokesperson said: "We’ve always been clear that the uplift to universal credit was temporary. It was designed to help claimants through the economic shock and financial disruption of the toughest stages of the pandemic, and it has done so.
"Universal credit will continue to provide vital support for those both in and out of work and it’s right that the government should focus on our plan for jobs, supporting people back into work and supporting those already employed to progress and earn more."
Ms Fiaz's comments follow East Ham MP Stephen Timms, who in August appealed to the government to keep the uplift.
However, the government spokesperson pointed to £400bn worth of pandemic spending across the UK to protect jobs, livelihoods, businesses and public services.
Nationally, more than £9bn will have been spent on the universal credit uplift by the time it ends this month.
Children in households where every adult is working are about five times less likely to be in poverty than households where nobody works, according to the government.
Its plan for jobs scheme aims to support people long-term by helping them learn new skills, increase their hours or find work, the spokesperson said.
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