Pressure is mounting on the UK Chancellor to lift the two-child benefit cap at the the next budget.
Campaigners MPs from various parties are warning that a delay in lifting the cap will keep hundreds of thousands of children in poverty.
Reports suggest that Labour could be set to lift taxes and cut public spending to fix a black hole in the budget.
Higher than expected government borrowing has also increased the pressure on Ms Reeves, who would have to find an estimated £2.5bn a year at first - rising to £3.6bn a year when fully rolled out - to lift the cap, according to the Institute for Fiscal Studies (IFS).
A number of MPs have hit out at Labour for not lifting the cap already, including their own Kim Johnson, who said: "It is disappointing that Labour is not leaping at the opportunity to axe the two-child cap and immediately lift 400,000 children out of poverty."
Former shadow chancellor John McDonnell has also been critical of the party which he is currently suspended from after voting for an amendment calling for an immediate end to the benefit cap.
He said: "Children are living in poverty now, many classified as facing destitution.
"Delaying action on lifting children out of poverty cannot morally, economically or politically be justified."