The Work and Pensions Secretary has resisted calls from politicians in each of the four UK nations to halt the planned cut to Universal Credit (UC).
Dr Therese Coffey said it was right to focus on supporting people back into work now the economy was getting back on track.
The £20-a-week increase to UC payments, introduced as a temporary measure during the coronavirus pandemic, is due to be phased out from late September.
Dr Coffey was responding to a letter issued by cross-party committees from Westminster, the Northern Ireland Assembly, the Welsh Senedd and the Scottish Parliament.
They had called on the government to make the higher rate of payment permanent.
In her reply, Dr Coffey said: “Now the economy has reopened it is right that the government should focus on supporting people back into work and supporting those already employed to progress in their careers.
“Our ambition is to support two million people move into and progress in work through our comprehensive £33 billion Plan for Jobs.”
Stephen Timms, Labour MP and chairman of the Work and Pensions Committee, said the Government must “change course to prevent severe hardship for many thousands of families”.
He continued: “The £20 cut will plunge hundreds of thousands, including children, into poverty. Instead, the Government should extend the lifeline beyond September.
“The Secretary of State’s dismissive response to our letter suggests that the government is still in denial about the impact of ending the increase.”
Shadow work and pensions secretary Jonathan Reynolds said: “The government’s £1,000 a year cut will be a hammer blow to millions of working families, hitting the lowest paid hardest and hurting our economic recovery.
“Time is running out for the Conservatives to see sense and cancel their cut to Universal Credit.
“Almost half of those hit by this cut are in work – to claim there is a choice between cancelling this cut and getting people back into work is simply wrong.
“Labour would maintain the uplift until we can replace Universal Credit with a fairer social security system.”