Rishi Sunak is refusing to rule out slashing Universal Credit by £20 a week next April.
The Chancellor is understood to be “open to the idea” of keeping a special one-year Covid rise in the benefit.
But with weeks to go before ministers must confirm benefit rates for 2021, he is holding out on pledging the cash.
Treasury sources say it will “depend on where we are” in “terms of the crisis” of the pandemic.
The Government announced a one-year, £1,040-a-year rise in Universal Credit in April to help households through the coronavirus crisis.
The change massively boosted the standard allowance for singles over 25 from £318 to £410 a month.
Since then the number of people on UC has doubled to 6million and many have only ever known the higher rate.
Tory MPs, Labour, experts and even a former Work and Pensions Secretary want the £20 rate to stay.
Ex-welfare chief Stephen Crabb told the BBC: “We are on course to cut that money back in just a few months time and for me that's just unconscionable.
"You can't give money to some of the poorest people in the country and then go out publicly and celebrate that fact.
“And then say 'oh by the way, even though we may still be living with the consequences of the pandemic next April we are going to cut that money back by around £20 per week, £100 per month’.
“That's going to be a much bigger headache for the Government than school meals."
The Joseph Rowntree Foundation think tank warned 16million people will be hit if UC is cut back again in April.
The think tank says 700,000 would be pulled into poverty, and 500,000 already in poverty would enter "deep poverty".
A Treasury source said: “The Chancellor is open to the idea but it depends on where we are in spring next year in terms of the crisis.”
The Chancellor will deliver a one-year Spending Review for 2021/22 on November 25 which is expected to warn public sector pay must be reined in.
The Spending Review may not address benefit rates but they are expected to be confirmed separately next month.
Benefit rises are usually based on September’s inflation rate - and if so, they will rise by just 0.5%.
That spells a grim year for millions of people on old-style ‘legacy’ benefits, most of them disabled or long-term sick, who did not enjoy the £20-a-week boost.
Ministers have refused to raise jobseekers' allowance and ESA by £20 a week despite UC getting the boost.
Instead the basic rates of those two benefits rose by just £1.25 a week, to £74.35 for over-25s.
